Since I have done this instructable, I have made diagrams on how to use a socket to switch out crystals and how to use a switch to change speeds. Those diagrams can be found here http://forums.modretro.com/viewtopic.php?f=40&t=114
Step 1: Tools Needed
soldering iron (30- 40 watts is fine)
crystal (14mhz or 16mhz is recommended
triwing screwdriver or small flathead screwdriver
basic soldering skills
a game boy color (duh)
rosin core solder
Step 2: Taking It Apart
However, if you do not want to spend 5 bucks, you can use one of those mini flathead screwdrivers. The trick is to put the tip inbetween the three intersections on the screws. Then, if you did it right, can take out the screws.
Now, after you have the case off, you can get to the insides. There are screws atatched to the board, but we do not need to take these off.
Step 3: Locating and Removing the Old Crystal
To remove the crystal, get a small pair of vice grips, and clamp the crystal with it. Move the vice grips back and forth, and, if done correctly, the crystal will come off. Be careful not to break off any surounding parts though. Now there should be some visible contacts where the crystal was attatched. This is where we will solder the new one to.
Step 4: Adding the New Crystal
Go out and get yourself a 14 or 16mhz crystal for the game boy. Don't go much higher than 16mhz, though, as doing so would make games unplayable, and could possibly fry the system, which we obviously don't want to do. To save some money on the crystals, take apart some dead electronics, such as crashed computers, and find a crystal in there.
Now we need some wire. You only need two 3 inch wires, but make sure they are not too thick, as it could make it hard to fit it in the case. Now solder the wires to the crysal's leads, and then solder the the ends of the wires to the contacts where the old crystal used to be. It doesn't matter which leads you solder to which spot, because crystals have no polarity.
Next we have to find a place for the crystal. I found that near the top of the case, there is plenty of room for a crystal to fit.
Step 5: Putting It Back Together
Turn it on, and play your games at a faster pace. If it does not work, check your connections. It may be a cold solder joint. To fix this, just re-melt the solder on the connections.