Here's a poor mans method:

1. Get a 30ish watt soldering IRON. Guns will not work. A trip to wally world will get you one for 5 bucks.

2. Heat/melt the solder/wire. Make sure you can get a good, clean place to transfer the heat. DO NOT APPLY HEAT FOR MORE THAN 5 SECONDS!!! You will fry your electrics if you hold the iron on too much.

3. When the solder/wire is molten, quickly tap the esc on the desk/table. if the solder is hot enough, it will fly out when you tap it. Then you should be left with a nice, clean hole to insert a new wire into. If it doesnt come out, let the esc cool for 5 minutes, and try again. Try taping it harder, or getting the solder hotter.

If you are in doubt, let someone else more experienced do it. Frying an ESC from poor soldering is inessicary.

Cheers!