A friend of mine has a Mr Gimmick repro cart that he says has the hardware for the famicom expansion audio.  I am going to do the expansion audio mod to my front loading console soon so we can hear the difference, but I am wondering if there are any other mods or maintance that I should do while I have it apart.  

This is my original NES from 1987.
 

id disable the lock out chip as well .. if you have everything already apart ... takes about another 1 minute to do that. do a quick google search ... super easy.