Directions to Make an Airsoft Halo M6G Magnum?

I was playing Halo, and was wondering if i could modify the appearance of an airsoft pistol to match that of the M6G Halo 3 pistol.  Are there any instructions, that are easy for a newbie on this stuff to follow, on how to modify a gas blow-back airsoft pistol's appearance?  Thanks, bye.

NOTE: It needs to still work