Are you good at soldering? Because the modification of adding a second analog stick is quite hard. There are very very tiny little pins that you have to solder, and it is not a mod that should be tackled as your first mod >.< (Knows from experience). There are a lot of really talented modders for hire here on Acid Mods, and the pricing all seems quite fair. So if you are able to work something out I would highly recommend you contacting one of them, or having a person whom is good at soldering there to assist you. That way you do not disable your system. (It'd be cheaper to pay to have that mod done than replace the PSP)
Just my two cents
-TwisT