The National Football League slips into a new season and a new era this week as the opening of training camps formally sounds the closing bell on a busy offseason. It began with familiar sights, Joe Montana accepting an MVP trophy and the San Francisco 49ers standing in the Rose Garden with President Bush.

But while pro football's new decade may have dawned that day, it was only the beginning of a rush of activity that would include the signing of a $3 billion television contract, adoption of a new schedule and playoff format and tough new rules against steroid use.

There was also the hiring of a new anti-drug chief, the hatching of an international spring league and the usual coaching shuffle: The Atlanta Falcons (Jerry Glanville), Houston Oilers (Jack Pardee), Phoenix Cardinals (Joe Bugel), New England Patriots (Rod Rust) and New York Jets (Bruce Coslet) all handed their headphones to new men.

And there have been the continuing story lines. Pro football's players and owners haven't had a labor agreement since Oct. 15, 1987, and the two sides begin this season farther apart and angrier than ever.

Plus, there have been a couple of interesting Al Davis news conferences. Having waged an expensive war with the NFL over whether he could move his Raiders from Oakland to Los Angeles in 1982 (he won that one), pro football's itchy-foot now appears ready to move them back.

Yet what a lot of people likely will remember about this offseason is that it marks Paul Tagliabue's first full year as commissioner and comes at a time when the league is taking its exposure and marketing up another notch.

"Show biz," New Orleans Saints President Jim Finks said. "If you see that that's important, you've broken the code. The Turner network is already hyping this fall's football."

There will be an additional 14 games on national television, a couple more playoff games and a preseason schedule that includes stops in Tokyo, Berlin and London. Bricks had just begun to come loose on the Berlin Wall when the NFL was plotting a marketing strategy to bring not only the game but also T-shirts, key rings and helmet lamps.

All of this is a prelude to the new World League of American Football, which will debut next spring with franchises in San Antonio, Memphis and Orlando as well as Milan, Frankfurt and London.

"We are very fortunate that most surveys rank NFL football as America's favorite spectator sport," Tagliabue said recently. "This new schedule format allows us to expand our share of the annual sports calendar. Television revenue was an obvious factor, but we also are sensitive to possible overexposure of our sport. Both were weighed in our decision."

After sealing new television contracts with CBS, NBC, ABC, ESPN and TNT, the NFL has increased each team's slice of the pie about 93 percent, to approximately $33 million a season. The bottom line for fans is that they'll have the usual smorgasbord of games on Sunday afternoon as well as national specials on Sunday and Monday nights. Expanded Playoffs

The new schedule format is simple. Each team will play its 16 games in 17 weeks the next two seasons, then play 16 games in 18 weeks in 1992 and 1993. There now will be only one week -- instead of two -- between the conference championship games and the Super Bowl. The regular season begins Sept. 9, and coaches generally have reacted favorably to the idea of having a week off, although almost none seems happy about when he gets the week offf.

"It can be good," Redskins Coach Joe Gibbs said cautiously.

It'll also be easier to make the playoffs. Two additional wild-card teams will make the playoffs, increasing the total number of teams in postseason play to 12 (six division champions, six wild cards).

"It's a very positive thing," Finks said. "It may not mean much to the Giants or Redskins, who think making the playoffs is no big deal. But in Kansas City, Atlanta, San Diego and places like that, it's big-time stuff. It keeps the interest up; it makes so many of the games at the end of the season more important." Plan B

The NFL appears to have cashed in a gold mine with Plan B free agency, the process whereby a player left unprotected (each team can protect 37) is free to sign with any other team. Plan B was one of the reasons the Green Bay Packers enjoyed a remarkable turnaround last year, and this year 184 players changed teams -- 58 percent of them going to teams with losing records last year.

Every team except the Indianapolis Colts signed at least one Plan B free agent, with the 1-15 Dallas Cowboys leading the way with 16. As many as half those free agents may end up with starting jobs.

They weren't alone. The Packers spent heavily on Plan B again, signing 13, while the Redskins, Chiefs and Jets signed 12 players apiece.

"It has given teams another way to improve themselves," Redskins General Manager Charley Casserly said. "If your ownership allows you to spend the money and your football people do a reasonably good job, you can definitely improve yourself." The Champions

Once the season starts, eyes again will be on the 49ers, who could become the first team in history to win three straight Super Bowls. They appear to be well on their way, again spending more money and living more extravagantly than any other team.

That spending began with the ceremony to distribute their Super Bowl rings. Team owner Edward J. DeBartolo Jr. didn't just pass them out; he rented a 747 and flew his players and their wives to Maui for a weeklong vacation that cost him about $1 million.

One of their few worries is star nose tackle Michael Carter, who underwent a high-risk foot surgery that has left team officials unsure of his future. No problem. The 49ers dipped into the Plan B market and spent $750,000 to get Buffalo's Fred Smerlas.

Their other question is in the secondary, but they used Plan B (and about $700,000) to haul in New Orleans safety Dave Waymer and Cleveland's Hanford Dixon.

Tagliabue expressed concern on draft day that the system wasn't supposed to work to make good teams even better, but no changes are planned for 1991, at least for now. Labor

Both players and owners probably would like a collective bargaining agreement, if for no other reason than to end the parcel of court cases. That appeared a possibility a few months ago when negotiations resumed briefly, but it fell apart over the issue of free agency.

The NFL Players Association says there must be some system of free agency because it's the fairest way to determine salaries. Management disagrees, saying that most players want better benefits and salaries, not the right to change teams.

Now, the NFLPA appears to be fighting a war even closer to home. Former Dolphins great Larry Csonka has announced plans to form a competing union and is collecting the necessary signatures. Upshaw says Csonka is a management puppet. Finally . . .

Some NFL executives say they worry about overexposure, about the public finally growing tired of football. They realize there'll be college football on Thursdays and Saturdays and pro football on Sundays and Mondays. Still, for everyone sounding a note of alarm, there are others who say these are the glory days -- so enjoy them.

"We're on all three major networks and two cable networks, so overexposure is a concern," Finks said. "I'm concerned about too much baseball and basketball on television too. But right now there's a market for it. People obviously want it. The networks buy it because they're able to sell it."