New User - Bike Squashed by Transit Van! :-(

Hi All, just want to say hi, I am new here so be gentle

A couple of weeks ago a transit van decided to park itself on the back of my '01 Daytona 955i, the insurance gave it a cat C write off as its cosmetic damage only so I now have the bike back and a pile of cash.
On the inspection sheet they are saying that it needs a new rear frame. Now, I have loads of experience with mechanics as I used to build minis as a hobby so I am not a novice but the question I have is...

How do I determine if the rear frame is indeed twisted or otherwise broken? I have visually inspected it and I cannot see any signs of weakened welds, paint crack of evidence of movement. The left hand rear panel doesn't quite sit right next to the middle panel near the seat but I think that is because the rear panel is twisted.
The other panels on the rear are not quite right at the top over the rear light but again I suspect the plastics have been distorted rather than the frame. What I need is a relatively definitive answer before I go pulling it all apart.

Also from a safety point of view, if the rear frame is slightly off will it affect the ride? On looking the suspension etc is all connected to the front frame so in my opinion it shouldn't but I would like to know from someone more experienced than myself.

Thank you in advance!

Many thanks
Andy