Here's some begginer tips,
Open the mechbox inside a large ziplock bag, incase things do explode, you won't have to spend hours looking for the parts.
Before you open the mechbox, take a small pair of needle nose pliers, and pull back the anti-reversal latch, That'll relieve alot of tension inside the gearbox, and reduce the chances of a "KABOOM"
go to
www.mechbox.com and watch a bunch of videos of people upgrading their gun.... And learn this .gif
Better .GIF:
http://www.mechbox.com/site/mechbox/...box-works.html