I just replaced mine last weekend. Same issue the molding let go so I could not put the boot on anymore. The nuts are hard to get to for sure. There is one between the quarter glass window and the body panel at the front of the trim. I got to that with a small socket and ratchet. There is another one 1/2 the way along where the top connects to the body. And the last two are the real trick one is just at the corner as the trim goes up over the rear deck and the last is right before it connects to the back trim. They are a pain to get to unless you know what you are looking for. You really have to feel for them. I would advise putting in a larger washer if you can, the holes are soo small for the amount of pull a boot can put on the trim. I didn't want it to pull the nuts through or break the mental mounts.
If you already have new trim then I would carefully break the other mounts off so you can see the full picture then you can see exactly where they are and then unscrew them from the top using the broken plastic. The trick is then getting the new trim on. No special tools just patience.
Good luck.