I wanted to change the look, to customize my Strat, so I found a torise-shell pick guard on eBay for about $10. I checked out some instructions online, and decided it would be easy enough to do myself.
The MIM Strat, before:
First, I had to remove the strings, and then unscrew the 11 small screws holding the pick guard to the body.
Using a small ratchet, I removed the nuts from the tone and volume potentiometers:
Lift the pick guard, and slide a piece of paper underneath to capture any springs or screws that may drop.
I had to unscrew the screws that hold the pickups in place, and remove the pickups. This is the tricky part, because the pickups, potentiometers, toggle switch are all connected via wires and a small drop of solder. So I didn't want to pull anything loose, anything that could affect the sound of the guitar.
I relaced the parts into the new pick guard, and replaced the pick guard back on the Strat.
However, th new pick guard didn't line up perfectly. So I had to drill out about 6 more holes in the body to secure the guard.
The result is a Tex-Mex like-look: