Trunk was Slammed & Won't Open, Tail, License Plate & 3rd Brake Lites are OUT

Sorry to say, I agree with the manager on this one. You should be able to slam a trunk lid without causing damage on any car. You've never seen a warning label telling you to close a trunk lid gently or the car will fall apart. Cars aren't built like that.

I can't agree with the mechanic, but it's not fair to find fault without being able to see the car myself. The typical thing to look for is a metal linkage that popped apart. You didn't say if you tried to open the trunk with a key, a remote key fob, or a switch inside the car. Normally the lock cylinder in back works with a different linkage than any remotely-activated device, so if a linkage came apart for one of them, the other one would still work.

Since it sounds like some lights aren't working either, that commonly occurs when a wire or terminal in a connector is corroded off. Slamming the trunk didn't cause that corrosion. It just hastened the failure that was going to occur anyway. The store should not be liable for that. The same problem could have occurred if you hit a big pothole.

The reason the guy slammed the trunk so hard is very often that's what it takes to get them to close. We have also heard the stories of people getting angry because the guys were too gentle at first, and it took multiple attempts to get them to latch. Up here in Wisconsin where we throw a pound of salt on an ounce of snow, dust in the summer and salt in the winter can get ground into the paint and will be there permanently. (That's why we never write "wash me" on someone's car). People have complained about that too from those multiple attempts at closing the trunk.

You know very well that a trunk on any car is made to withstand slamming without damage to mechanical parts or electrical wiring. Age played a big factor here. I know this all too well because my daily driver is a very rusty, trusty '88 Grand Caravan. There's probably only a dozen like it left in Wisconsin. Plastic clips that hold door linkages deteriorate and crack. Rubber door seals get chewed up. Nothing fits like it did originally. We know things are going to break. It's just a matter of when and who did what when it happened.

I'd let the store manager off the hook. It's the repairs I'd be questioning. How did tail light housings, bulbs, and so much get damaged and need to be replaced. The stuff you listed is typical when a car has been rear-ended. Slamming the trunk isn't going to cause all the stuff on your list. I'm happy to explain why many mechanics are blamed unfairly for being dishonest, but I won't defend one who appears to be taking advantage of the situation. The impression I get is that's what took place here. In Wisconsin you have the right to ask for your old parts back. I suspect the law is similar in most other states. You might want to have a different shop examine those parts and give you their opinion. To get an impartial opinion, do not tell them which shop replaced the parts or why. They could be influenced to slant their findings in favor if they're friends with that first shop, and they could try to make them look bad if they aren't on friendly terms.