Why not have it sand blasted? If you add up even 1/3 of the hours you would have in sanding or stripping you could pay for blasting, not to mention blasting is going to do a better job at removing paint from places you would find extremely difficult to get to with a sander....

Get ready for a lot of work...if you are sanding. It all depends on how far you want to restore the paint job. If all you want to do is scuff the original paint, a light touch with 320- to 400-grit paper will work. If you want to take it down to bare metal, 80-grit is a good option. If the car has some mean ol' nasty paint consider a 40 or even 24 grit paper. If you don't need to work your arm muscles, consider using a rotary sander but be careful with what paper you use, you don't want to burn the paint or your sander. Good luck and have fun!!!!