You have a lot of work ahead of you,,, it isn't complicated just work.
If it was me, I'd probably screw the roof together using pieces of thin plywood, then get it positioned over the body.
Once the roof is close to correct location connect the cleanest breaks with screws and ply same as roof. It will be a puzzle ad to when to join which piece. Step back and look at the big picture making sure the shape is staying correct.
I did a small project using some of these principles starting at post 187 here
https://www.fiberglassrv.com/forums/...r-55601-8.html
Get started dont quit,, it will look great!
Fred