depends on year/model/mileage/condition and diff prices

If the car is in good condition over all, the damage was only in rear end, and the price difference between keep and not keep is only hundreds, I'd choose "keep it". As I know I can always get the same body parts from junk yard. If trunk is scrambled, you can cut it off and weld on the replacement.

Well, you need to be a good DIYer.