from an expert. when you sand it make sure you wetsand it with either 500 or 600 grit. keep it wet all the time so you dont make any deep scratches. where ever you go to get it painted, will(if they're a good shop) tack it down like you're supposed to rid the surface of any dirt/dust/grease so the paint will adhere properly. make sure you wetsand the primer also to a smooth finish unless you want flaws showing through the paint.

last thing, be patient with it dont rush.