i got a question about the G&P metal hop up im going to be getting one for christmas along with my metal body for my m4 and i was wondering if anyone knew of a website that showed how to put one together or if anyone knows how to put one together here

I just put together one myself. Easy money. Only easy part of my G&P body install.

does it come with instructions

I don't know if they come with instructions if sold alone. It's really sort of self explanatory.

Looking at this picture, you can see how it goes together.
http://www.blacksierra.net/review_photos/src_416/full/IMG_20.jpg