[CerberusNet]

Jeez hope you didn't pay him to #*?! your gun up! If you live in the area you could drop it off to me, I deal G&G and KJW guns. I'm sure whatever he did isn't to difficult to undo. If not, go back to him and demand something be done about his horrible smithing skills and that he gets a thesaurus and re-learns the definition of "Fixing" lol
Hope you get what you need.
Also wanted to add, a leaky mag is usually a simple fix. In most cases you just need to get some silicon gel for the orings they may have dried up. If there is a crack in the casing then you would have to replace or weld it shut. The best way to find the leak is to dunk it in warm water and search for bubbles.