Several times in this Instructable, I'll be referencing the How-To: Make a Wii laptop page by Benjamin Heckendorn (thanks!). He has some VERY good tips on complete Wii disassembly as well as de-soldering.
Here are the tools you'll need:
A Wii (duh!)
An original NES
Small Phillips screw driver
De-soldering braid or de-soldering iron
Hot glue gun
Dremmel tool or drill with a fine tip drill bit (1/16" and large drill bit (5/16")
Wire (preferably multiple colors, I used 18AWG, but probably should have gone thinner in retrospect)
SD Reader you don't mind destroying (or SD port ordered online)
2 momentary switches (preferably 'micro' switches)
Step 1: Disclaimer
I hold no responsibility for broken parts, things not working, damage to your console, or anything else should you attempt this project.
I consider myself to have great soldering skills, and have worked with small electronics (read in: 30AWG wiring) in the past. If you are uncomfortable with [de]soldering fine electronics, I would recommend having someone else solder for you, or put this project off until your more familiar with this type of work.
*When I first started this project, I had no way to take pictures of my progress. I will try to be as detailed as possible for the first few steps.