Too bad about the grille, but looks pretty good for the money. It looks like the rubber bumper strip on the driver's side below the headlight is coming off. In fact, that looks like a nasty little dent in the lower driver's side fender ahead of the wheel. In fact, in this photo, you get a better sense of the driver's side damage, and it looks like the grille damage, bumper damage, and lower fender damage are all due to the same accident. The bumper around the driver's side headlight is pushed up. Suddenly $900 seems just about right.
That 'fender' damage you are seeing below the bumper rib strip is actually part of the bumper cover, which wraps around and goes all the way to the wheel opening. So I think the fender (with the wood grain) is OK. Might need some hidden stuff, like a header panel, but shouldn't be that big of a problem to repair.
What's a '91 doing with a 3.1. I didn't think that engine was offered in the A body until 1994. A '91 shouold have the 3300 Buick V6 (imo, one of the best V6s ever made), shouldn't it?
3.1 = 2.8. Aside from head gaskets sometimes failing, the all iron engine is as reliable as an anvil. It looks like a small block Chevy.