"acetone will remove the painted on type of stripe. Now, my question is, on my black Crown Victoria, once you remove the stripe it has these little ridges where the machine paints on the stripe. What does anyone recomend using to buff these out, and should it be by hand or machine?"
Acetone will soften paint, so be careful. The little ridges i would recommend wet sanding with 2000 grit and then a machine polish. If you are leary about wet sanding try some machine polishing on one area, and check your progress.
"I think Eastwood Company made a buffing-type wheel for a drill that would take pinstripe tape off without harming the paint."
3M and a few other companies make them, and they do work fairly well, you could also try an auto body supply shop. If the wheel leaves rubber residue behind , a mild solvent removes it.
"Corey Bit Spank, if this decal has been on the car for 3 yrs., isn't there a chance that the paint under it will be a different color than the rest of the paint?"
I think the color difference would be more from scratches and swirls. You might have to polish and wax.
"My friend is inquiring on how to remove a 5" by 2" pinstripe (sticker/decal, I'm guessing) from a 3 year old maroon colored car. (on the rear quarter panel) I did a search but really got no solid advice on how to get it off and get whatever residue that may be left cleaned up. Help a fellow out"
The heat gun or hair dryer work well. I would take a plastic razor blade or make one out of a plastic picnic knife. Take the heat gun and heat the picnic knife edge until the little serrated edge is smooth. Heat the decal and try to pick the decal off (might leave alot of glue behind) or heat the decal and scrape the decal off with the plastic blade, you'll know when temp is right. Do not over heat. When the decal is off, take a mild solvent ( i generally use Varsol) and wipe it till gone with a soft cloth or paper towel if polishing. If you have lots of glue, scrap off with the plastic blade.