You must let me do it!

Seriously, though, it isn't too hard if you have soldering skill. Hacking the analog triggers (the L and R buttons) is probably the most difficult aspect. Other than that, wire one common ground, and a wire for each button and direction.
(You end up with 12 wires in all- A, B, X, Y, Start, L, R, Up, Down, Left, Right, and Ground.)