Before one can think to say, "Don't get up," James Stacy is hopping across the floor of his hotel room so he can turn off a clattering TV set. He is hopping on one leg because he only has one leg, and only one arm as well.

In September of 1973, the motorcycle Stacy was driving up Benedict Canyon Road in Hollywood was hit by a car coming down. Stacy lost almost all of his left leg and left arm in the crash, and his acting career seemed to be over. But tonight he will appear as an amputee wounded in Vietnam in "Just a Little Inconvenience," an NBC TV-movie at 9 o'clock on Channel 4.

It's the most literal kind of type-casting, perhaps, but Stacy's performance is powerfully commanding and straightforward. Director Theodore J. Flicker shows little feel for the visual idiosyncracies of television, and the script Flicker wrote with Allan Balter lacks resonance, to put it kindly. But Stacy carries the show, and makes "Inconvenience" far more than just another TV tearjerker.

Getting the film made was not easy for Stacy. Except for a part in a movie called "Posse" which he says he'd just as soon forget, he hadn't done any major acting since the accident. His career had looked promising after two years (ending in 1970) in the above-average Western series "Lancer."

But he found himself in no demand as an actor afterward.

"My agent went around to all the networks a couple of years ago to see about a movie or a series or something," Stacy recalls. "They all said, 'No, it's - ' 'No, it's - ' They're weird, you know. My agent would use Raymond Burr in 'Ironside' as an example that audiences could accept this, but the networks would come back and say, 'But everybody knows he's not really crippled."

It was Stacy's friend Lee Majors, a costar in the film, who got Stacy the part in "Inconvenience" and helped him keep it when Stacy was having re-adjustment problems during the filming in Alberta, Canada.

"The first couple of days, I was apprehensive, I was fighting it. I got into a big fight with Barbara Hershey, who plays the girl I fall in love with. And they wanted to fire me. I said, "How are you going to replace ME?" They said, we'll get somebody and tie their leg behind them and put their arm up. I said, 'Okay,' I was just scared. Ted, the director, thought the script was so strong, and I wanted to add a few little touches from my own experience, but I did't go about it right, and he wouldn't give an inch.

"So this was a Friday, and Saturday they suspended shooting, and Sunday I was packing to leave. Lee walks into my room and says, 'You really screwed up, didn't you?' He asks me, 'You want to be in this picture?' and I said, 'Yeah, I want to do the film.' He left and one hour later he called and said, 'All right, you're doing the picture, we start shooting again Monday, be a good boy.'"

Ironically or not, there are scenes similar to this in the film, which is the story of a Vietnam veteran who blames his buddy for the land-mine that blew away his left arm and leg.

At one point, the character he plays is describing to Hershey how he felt after the land mine blew up. Stacy says he contributed this monologue based on his own memories of how he felt immediately after his accident.

"I was awake, I remember that. There was nobody around and a dog barking. I was lying there saying to myself, 'Oh (expletive), did I get out of that one?' I felt my face, it was still there. But my left arm didn't come up on my command. I thought, 'Oh (expletive), my arm's broken.' Then I looked down and saw a five-inch bone sticking out of my leg, and I thought, 'Oh (expletive), my leg's gone.' There was no pain, though, it was very euphoric. I could hear everything, I could smell everything. I passed out, came to, passed out and came to again. I remember thinking that I wanted to live."

Stacy spent three months in a hospital recuperating and many more months learning to adapt to this radical change in his life.

"It still affects me, sure, I still go back. It took about a year and a half to really say, 'Aw, the hell with it.' One problem was, I would do or be what I was before the accident, but it wasn't accepted by people, because they thought what I was doing or being was because of my loss. I had to adjust to that. If I just sat and looked a little bored, people thought I was depressed. If I argued with someone, they'd think it was because of my arm and my leg and that I was bitter, not just that I had opinions.

"When I dream now, I've got my arm and leg, I'm full. There hasn't been one dream where I have my loss. I think it's because of the phantom sensation. Because I can feel my arm. I can move my arm. I can feel my fingers - they're cramped becauseof the trauma, but I can feel them. I can still feel the bumper of the car hitting my knee, if I think about it."

As the amputee in the film, Stacy comes out of a shell by learning to ski. In fact, Stacy himself learned to ski - taught by Jean-Claude Killy no less - and also can scuba dive, water ski and do other physical activities. He hopes that "Inconvenience" will show others in similar straits that neither life nor movement need end for them.

At key moments, the film becomes a pretty stirring statement on fighting back no matter what form adversity perversely chooses to take. There is a long and painful sequence of Stacy first trying to get up on skis - falling, getting up, falling, getting up, falling, pounding his fists into the snow in rage. You don't have to read much into these scenes to find them meaningful even to nonamputees.

Stacy wants to write now, possibly produce, act if parts become available. After the initial difficulty, shooting "Inconvenience" - mostly in Canada - became a basically enjoyable trial, he says. Not all the production problems were terribly serious or psychological ones, either. For instance, the wife of Majors, whose name is Farrah Fawcett, occasionally interrupted shooting just by being around.

"They finally had to send her home," says Stacy, smiling. "She was just causing too much commotion. She's always saying, 'I must have privacy - privacy, privacy, privacy.' But she's still got her hair out there.' She's still out there smiling! I said, 'God, Farrah, put something on! Put a hat on, put some glasses on, disguise yourself.' But she wouldn't."