Your gonna want
M120 or PDI 150% to 170% spring
Bushings
gears(durability)
tightbore
your not gonna be able to wrap the mechbox in tape, not much room in there and it wont do much. Keeping your gun lubed is the best thing to do.
battery, 8.4 is good, but if you can fit a large battery in, your gonna be much better off. The mini batterys dont have much juice and are noticably weaker when compared to large batterys.
WGC is the way to go.
as for doing the upgrading, a local gun doc is a good way to go.
if not goto
http://www.airsoftplayers.com/guides.asp and do it yourself
read the guides through and if you think you can do it, go for it....its not as difficult as some make it sound. Just take it apart, and make sure you put everything back the way it came off.
Play a bit stock, but really, a gun that shoots 100 feet blows, so double it and have fun.
now rice that 36 out