go into 3dModelWindow>Show Object List and turn off the ones that are spheres.
then youll have to decide how to cut it so its easier to put together, dont just hit "auto unfold"
i would defanatly simplify the model in a 3d editor before attempting to unfold it in pepakura.
those spiky things are the glue flaps, pepakura like to make the flaps long by default,
go into Configuration>Flap Configuration>Change All Flap Widths , (around 5mm usually does the trick)
im working on a shotgun right now, and im 80% ready to release the finished pdo, (edited 3d model, per request)
ill also begin working on a AR soon too