CBS Entertainment announced yesterday that the three-hour conclusion of "Dream West" will now air on Sunday night, starting at 8 p.m. . . .

The concluding episode of the mini-series was originally scheduled to air last night. But the breaking news story from Libya Monday night an hour before primetime changed all that . . .

The two-hour Part II of "Dream West" was pulled from the Monday schedule at the last minute when CBS learned of President Reagan's address at 9 p.m. and the upcoming briefings by Defense Secretary Caspar Weinberger and Secretary of State George Shultz. A decision was made to give the full hour to CBS News . . .

With Part II of "Dream West" no longer feasible, CBS on the West Coast was contacted and a rerun of "Cagney & Lacey" was satellited to New York for tranmission over the network at 10 p.m. instead . . .

Earlier, CBS had aired "Kate & Allie" and "Newhart" in their scheduled time slots starting at 8. . .

Part II of "Dream West" was then moved to last night, preceded by a Bugs Bunny special. But where to put the conclusion? Tonight belongs to ABC (and CBS has been promoting a rerun of "Not My Kid," a cautionary tale of drug use among the young). Thursday belongs to NBC. Friday already belongs to CBS. And Saturday audience levels are much too low to satisfy advertisers . . .

Both ABC and NBC had less trouble with their big-ticket items on Monday night, amidst all the reports from their news divisions . . .

ABC joined "Hardcastle & McCormick" in progress at 8:03. After the president and the briefings, the network began the two-hour run of its scheduled movie, "A Winner Never Quits," at 9:39 . . .

Likewise, NBC aired "You Again?" and "Valerie" in their regular Monday 8-to-9-p.m. time slots. The network followed the president's address and further news reports with its scheduled Academy of Country Music Awards, which ran from 9:51 p.m. until 11:53 p.m. (The awards, which were to air live starting at 9 in the East, began on schedule. Eastern viewers saw the taped version, which West Coast viewers saw later in the evening) . . .

As far as the network news coverage of the attack was concerned, "ABC World News" and "NBC Nightly News" apparently shared a slight edge . . .

ABC Radio correspondent Liz Colton had called New York at 6:55 p.m. eastern time to report she could hear gunfire. Consequently, 38 seconds into the 7 p.m. feed of "World News Tonight," anchor Peter Jennings repeated Colton's report, and about 7:05 p.m., Colton's live telephone report from Tripoli went on the air . . .

NBC News' Steve Delaney was on the air with a telephone report from Tripoli on "NBC Nightly News" at 7:02 p.m. . . .

Cable News Network reported the attack at 7:10 p.m.

CBS correspondent Allen Pizzey and Jeff Fager, "CBS Evening News" executive producer in London, were heard at 7:13 p.m. via telephone to "CBS Evening News" reporting the sounds of battle . . .

All three networks stayed on the air with the news until 8 p.m. ABC News broke off its coverage shortly after 9:30, while NBC News continued until 9:53 p.m. . . .

In late night, NBC did a seven-minute wrap-up at 12:23 a.m. Tuesday and ABC's "Nightline" went on the air from 12:06 until 1:08 a.m. with Libya as the topic . . .

At 3:17 a.m. yesterday morning, ABC's Ted Koppel went on the air with an eight-minute report featuring the first TV coverage of the attack, provided by Libyan television. Similar footage was narrated by Bob Schieffer on CBS' "Nightwatch," starting at 3:40 a.m., and NBC News' Bob Jamieson gave a five-minute report on that footage, starting at 3:51 a.m. . . .

ABC, CBS, NBC and CNN all maintained a close watch on the story throughout the day yesterday . . .

Incidentally, NBC News reports that Mike Silver, a producer in the Rome bureau, leased a plane Monday and went looking for the Sixth Fleet, which was supposed to be off Sicily . . .

At 9 a.m. New York time, he spotted the U.S. armada -- heading for Libya . . .

On his return to Rome he notified New York, which contacted Pentagon correspondent Fred Francis. When he told Navy sources of the report from Silver, he was urged "to use your conscience" . . .

NBC News in New York went along with the appeal to national security considerations, meanwhile obtaining an open telephone line to Delaney from the London bureau and later another line direct to him in Tripoli from Manhattan . . .

The only mention of the fleet on "NBC Nightly News," prior to the actual attack reports, was speculation it was still off Sicily . . .

By the Way"

CBS Evening News" will begin its five-night feature on what the world will be like in the year 2001 all over again next Monday night . . .

Viewers of the first (6:30 p.m.) feed of the newscast on Monday saw the clever opening segment of "2001," but it was cut from the second (7 p.m.) feed as the attack story took over . . . and CBS News officials decided to give the feature a fresh start next week . . .

"Entertainment Tonight" cohost Mary Hart, in town yesterday, revealed that her manager, Jay Bernstein, will be joining Paramount Television May 16 to begin work on a situation comedy pilot starring Hart . . .

Bernstein has been executive producer of the Mike Hammer series for CBS, which his Jay Bernstein Productions and Columbia Pictures Television produce . . .

A new two-hour movie, "The Return of Mickey Spillane's Mike Hammer," airs Friday night on CBS. There's a faint chance that if the ratings are good, the series could return to the network next fall . . .

Bernstein's deal with Paramount Television reportedly calls for other projects besides the Hart sitcom . . .

Hart, who will have been with "ET" four years in August, says it's possible she could do the sitcom, if it's accepted, and continue with the weeknight syndicated show . . .

We hear that NASA will today announce the list of journalists being considered for a shuttle flight into space sometime in the future . . . and that NBC's space correspondent Jay Barbree and NBC's science correspondent Bob Bazell both made the cut . . .

Apparently not on the NASA list: CBS' Walter Cronkite . . .