You didn't say what kind/condition of car you had.
Depending on outcome, if you wanna fix it yourself:
1. Clean area of all dirt, wax, etc.
2. Wet sand with 1500 paper.
3. Using Touchup paint (color code matched) and an artists paint brush, paint a minimum of 12 coats of paint into the scratch (the number of coats is relative to the depth of the scratch), letting the paint dry at least 30 minutes between each coat (you're using the paint as filler, don't worry if the paint in the scratch seem higher than the paint on the body).
4. After you have enough paint in the scratch, wet sand first with 600 grit, then 1000 grit, and finally with 1500 grit. Sand until you cannot feel any surface deviations where the scratch is (don't panic, you will still be able to see where the scratch was, we're not done.)
5. Wait 2 hours and then paint 3 coats of touchup clear coat (again using the artist's brush). After dry, wet sand with 1000 and 1500. Sand until you cannot feel any surface deviations where the scratch is (don't panic, you can still see it, we're still not done.) When finished, there should be just the slightest hint of a `mound' over the length of the scratch.
6. Leave it alone for 48 hours.
7. Now, wet sand with 1500 until you can no longer see any hint of the scratch. Then finish with a 2000 grit wet sand. Wash well...
8. Compound with Meguiar's #2, using a clean buffer wheel. Do this twice, then use Meguiar's #9 (swirl remover). Be sure to wash the area with soapy water and rinse it between each change of buffing. Change to a clean buffer wheel and use a good Foam Cut. Then glaze by hand with Meguiar's #3.
Ripped from
http://www.gnttype.org while I was looking for ideas of what to do with a sagging headliner on an old car I picked up