The entire tail light assembly will need to be replaced. They are expensive if you buy from Jeep, several hundred dollars. However, there are quite a few good quality after market assemblies out there for around $50, give or take. You can find them at rockauto.com or some of them are even available on Amazon.

Plenty of taillight assemblies for an 06 Liberty on Ebay.com for about $45. As long as the surrounding bodywork is fairly straight it shouldn't be difficult to change.

Replace the whole tail light, it won't be cheap, but to fix it correctly that's what you have to do. I'd check with a salvage yard, that will be your best shot to get your best deal.

Yes

So a few days ago I accidentally backed my car into a tree. Didn't do to much damage but my back right brake light and turn signal cover was smashed, exposing the bulbs. The bulbs still work but I've noticed that the whole thing is coming loose. What can I do to fix this? And any idea as to how much it would cost? Oh and the car is a 2006 jeep liberty.