Mags are very upgradeable (good number of choices for anything you want to up except maybe the x valve, which is always top of the line) The ule body will be able to fit on it also.
The rail you would need to buy looks to be a classic rail (just going off picture though but someone else should be able to shed more light on it).
Can't tell you specifaclly what it's made out of besides the body and valve. X-vavles are made out of aluminum.
2.going off the picture I would estimate around 100-130 maybe. But that's just my guess on it.
Someone else more knowledgeable will be able to help you and probably prove me wrong on everything i said
btw i found your adress.