lookin at a 77 280, what to check???

I'm gonna go look at a nice 77 280. I only got to see the outside, but it looks restored....it's sweeeeeeett looking. It has 125K on it and the guy is askin $5K. What should I be looking for, in the engine area, underside, areas that like to rust? sounds I don't wanna hear. I'm not too familiar with the the earlier z's so I'd apreciate some help on what to look for. What would the going price be for a this car in excellent condition?

thanks,
Josh