BAMBI LIN FINNEY has hit the big time. At the young age of 22, she has already been on the Tonight show and this week she's doing the local television talk show circuit: San Antonio, Tex., Monday and Tuesday, Washington, D.C., Thursday. What's remarkable about this is that Bambi Lin Finney is not a hot new talent. She's neither a movie star, nor an author, nor a comer on themusic scene. To hear her tell it, Bambi basically repairs teletype machines. At least, she says, that's what she wants to do when her current notoriety "dies down."

There was a time not so long ago when a pretty 22-year-old teletype repairer might get on television talk shows just because she was a pretty female doing a "nontraditional" job. But we've come a long way since then, and Bambi Lin Finney has to do just a little bit more to rate that kind of exposure.

It so happens that Bambi Lin Finney is also a sergeant in the Marine Corps. Or she was. She is also adventurous -- she skydives -- and not terribly modest, and rather competitive. Some time ago, she got the idea that women in the military are just as pretty as women in the Ivy League colleges. The upshot of that revelation is that ex-Marine Corps Sgt. Bambi Lin Finney has burst upon the world, like Venus in the shell, in the April issue of Playboy magazine. Her picture has caused at least as much of a splash as Botticelli's.

The Marine Coprs claims she has lost her credibility with the men and has discredited the corps. And for that, it has discharged her.

"I though I would at least get a letter of reprimand," she says. "I didn't think they'd actually go so far as to throw me out."

It all started out innocently enough, says Finney, who went into the Marine Corps straight out of high school in order to learn a skilled profession. "I thought I'd let them take care of me until I could take care of myself."

She received her basic training at Parris Island, served a year in Okinawa, and was most recently stationed at Twentynine Palms., Calif. She was to have been discharged in November. One day, she says, she was glancing through an issue of Playboy and and came across a pictorial layout of women in the Ivy League.

"I said, 'I'm as pretty as they are.' A friend said, 'Why don't you write them?' and I said, 'No, I couldn't do that.'" But, of course, she did write them, and she sent along a picture and her vital statistics, and lo and behold, she got a letter back from them saying "Call collect. We are interested."

The April issue of Playboy began arriving at homes of subscribers a couple of weeks ago and folks in Washington and at Twentynine Palms discovered what Sgt. Finney had done. "The first word I got was that there would be no repercussons. I was told by my commanding officer that 'all we want to do is keep you from being harassed by the rest of the troops and carry on a s normal.' Then about an hour after that I was called back into the office ans he said prepare to be discharged." To make things easier, the government gave her an honorable discharge last Thursday.

"The reason why we did it is standards," says Marine Corps Col. Art Brill. "We have a philosophy in the Marine Corps, a longstanding one, that a marine is on duty 24 hours a day and while there may be time for outside employment and outside activities, whatever activity is undertaken by the marine is to bring credit upon the corps and not discredit. It's without a doubt that every action a marine takes -- both good and bad reflects not only on herself, but on every marine wearing a marine uniform now, in the past and in the future. We think that kind of conduct cannot be condonded. It's as simple at that."

Finney was not the only military woman to pose nude for the April Playboy. There were three Navy Women and one each from the Army, Coast Guard and Air Force. Several of them have gotten called before their commanding officers, one had her duties changed, and one got a letter of reprimand, but so far ex-Marine Corps Sgt. Finney is the only one who has gotten in real trouble.

"I'm sort of enjoying all the notriety while it lasts," she says, "but when it dies down I'll probably go into teletype repair in San Diego."

"Overall, I'm sorry I got kicked out of the Marine Corps, but I'm enjoying the adventure of it all. I think the Marine Corps is wrong. They took me in and they trained me and they gave me experience and then over a picture that would have blown over in a month they lost nine months worth of work from me."

The corps lost nine months of work from Sgt. Finney, a blow it presumably can weather, and it has reaffirmed its image as being the toughest, stuffiest and most demanding of the military branches. You can get away with that in the Navy, toots, but not in the Marine Corps.

There are, of course, some significant questions raised by this episode: Was the Marine Corps within its rights to fire Finney for something she did on her own time? Would it have have fired a man who posed nude for a body-building magazine? What does this mean for women in the military? Did Finney really lose her credibility?

Some people are agreeing with Finney that what she did was "neat." Some people are offended. But it nothing else, she has given us an amusing episode that lets us ponder just how far we've come. Think of it: a Marine Corps sergeant getting discharged for posing nude in Playboy.