I have a friend who has a 2000 Grand Prix with the 3.1l who is having some problems with his car....im not sure on the mileage but I know that his fuel gauge stopped working, his AC vents are messed up, and now his door lock is broken. I think I know how to fix the door lock and I haven't really looked at his AC but I guess my main question is....

How do you go about finding out what exactly is wrong with the fuel gauge?

I don't know if it is a float in the gas tank, if its a sensor, ir if the needle is stuck. He is supposed to come over on friday and I am going to take a look at it but I am not really familiar with Grand Prix's....Hyundai's, Mitsubishi's, and Nissan's are kinda my forte.

But any help would be appreciated and woot woot this is my first post here.