It sounds like your putting honest effort towards your project, which is great. Of coarse you can find this stuff out your self by going to
GBfans.com and skimming through the forums. But I will give you a few tips, if you want to work with wood, the best is MDF. Its a type of fiber board, it cuts great, and sands easily. Using foam would be fine as well, but as you hopefully know that spray paint melts foam, so use Bondo and spread it on the foam so paint will not melt it. And one thing thats easy to make is the Cyclotron, the round thing with the four red lights, a normal cake pan is the perfect piece to replicate it. For the injectors on the pack, the gun handle and barrel can be made with goodole PVC pipe. I would also suggest using Seans prop plans for the pack. If you have any other questions I would be glad to help, but once more
GBfans.com holds all the information ones needs to build a pack.