How does david get his body back?

I believe there is a scene at the end of Prometheus that shows Shaw lowering his body down out of the ship after she zips his head in a bag.

how it got reattached?  No idea

Since we  know that they brought his body along for the joyride to Paradise...I'm sure David instructed Shaw on what to do. Either that or he figured out how to utilize the Engineer systems on board to patch him up...

That satisfies my curiosity, for now at least.

One of the current reviews out said we will see David's head on Paradise before it's reattached. I'm sure it will be addressed in some way, pretty big plot issue if not.. "Hey, his head fell back on". lol

The Engineers worshipped big heads. David shows up as a talking head. The Engineers fix David. Whatever happens next im unsure.