The side panels have 2 screws at the bottom if I remember and then they hook off by sliding them upwards. They have a metal clamp/hook that slides behind body.
Rear window is a pain. I removed it and re-sealed it. It was messy but in the end worked well. I also made a new wood surround out of ply and then varnished it to protect from damp (hopefully only condensation)
I think I originally wired for 6volt instrument lighting but it ended up more complicated than I thought (as I was using relays for lights). So I ended up taking a spur off the 12 volt which was easier.
You seem to be cracking on with it.