Never use a angle grinder for body work such as sanding snows,it will put deep scratches and gouges on the body that will be a nitemare to get out.

Go with a orbital sander and since your first question was for what tools to get if you have a decent amount of body work to do and you plan on doing it yourself then invest about $250 in a 30 gallon compressor to power the sanders that you will need to preform the body work.

Also go to the local book store and take a look in the auto section and you will find at least 2 or 3 good books on doing basic body work. I have a couple that i still reference even though i've done the body work on other cars i've done its still good to have the info on hand to reference.

BG