The Washington Redskins entered the draft business 7 1/2 hours after it began yesterday, selecting Don Warren, a 6-foot-4, 230-pound tight end who "lives in the weight room" at San Diego State, as their first choice in the fourth round.

"I'm so psyched up right now you just cannot believe it," Warren said a few minutes after his selection as the 103rd player in the draft, the seventh tight end taken. "Just get me on a plane. I'm ready to play tomorrow."

The Redkins certainly hope so. They had been expecting to take a linebacker with their first choice, but Kansas City took their first choice, Frank Manumaleuna of San Jose State, earlier in the fourth round. So the Redkins turned to Warren.

"He's just a great kid," said Redkin General Manager Bobby Beathard late in a day filled mostly with disappointment, the result of several trades for higher picks that fell through and the knowledge that every other team in th division had strengthened itself considerably before the Redkins had even had one choice.

"Don's played in a disciplined system that emphasizes the pass," Beathard said. "He has great hands, and he's a tough hard-nosed, aggressive blocker who will help our running game."

Warren, from Covina, Calif., was a two-year starter at San Diego State and caught 39 passes to lead team receivers in 1978. He made a good impression on many scouts during the East-West Shrine game last winter, leading all receivers with six catches for 180 yards.

The Redkins were not satisfied with the production from the tight end position a year ago. Starter Jean Fugett was hampered by a weak knee and caught only 25 passess, and reserve Reggie Haynes grabbed only two.

Fugett had another knee operation in January and enters the option year on his contract. Asked specifically if the Redskins were unhappy with Fugett, Beathard said:

"All I'm saying is that we need a tight end that will help our running game, and block and work. This is a big need of ours; that's all I'm saying."

Can Warren come in and start for the Redskins? he was asked.

"I'd hate to put that kind of pressure on the kid," Beathard said. "But we'll find out. He's going to be given the opportunity."

Redskin Coach Jack Pardee said, "Se've got to get more production out of that position. I hope we can keep three tight ends next year.Jean's knee is better now than it's been in a long time, but he's still got a lot of work to do. His contract situation has nothing to do with it (drafting Warren).

"Can he start? When you're talking about a rookie, I don't think you can say that. You hope he's got the ability, but there are a lot of adjustments a rookie has to make.

"But if you're looking to a fourth-round pick as an immediate starter, yoy'll probably be disappointed. That's kind of far-fetched."

"They haven't made me any promises," Warren said long distance from San Diego. "Bobby Beathard talked to me about three weeks ago and explained their tight-end situation to me. He said they needed a tight end, but so did a lot of other teams.

"Yeah, I spend a lot of time in the weight room - four or five days a week. I do a lot of running. It's always been a dream to play pro football, and the way I took at it, the hard work has just begun. This whole thing is just far out. Wow, I can't believe it."

The Redskins believe the competion in the NFC's East Division significantly helped itself on the first day of the draft.

"They're all improved, no question about that," Beathard said. "St Louis got (running back) Ottis Anderson, a guy we hoped wouldn't be playing in our division. Philadelphia got Jerry Robinson, one of the two best outside linebackers, and improved the kicking gane with Tony Franklin.

"The Giants didn't get the quarter back they wanted, but they got Ernest Gray, one of our highest-rated wide receivers. And the Cowboys got some good people, and they don't even need the help.

"I had a feeling all the day we could make a deal or two, but when that fell through, it is kind of frustrating. Yeah, it's been a frustrating day, but the kid we got is going to help us, and that's a good feeling."

Barring trades, the Redskins will have four more picks today inround four more picks today in rounds six through 12 - a seventh-round choice, one in the ninth and two in the 11th. CAPTION: Picture 1, Tom Cousineau, first player picked in the draft, holds up a Buffalo uniform; Picture 2, Mike Bell, a Colorado State tackle, is embraced by mother after being second man selected. AP