Keeley mods for SEM and Ultra are splattered all across the Internet. Monte Allums, you get it by buying his mod kits. Analogman...I think those are unavailable unless someone reverse-engineers them.
But the mod recipe's are the easy part. The harder part is kinda the Basic Electronics thingy...proper soldering technique, reading resistors and caps, identifying diode types and etc. It takes a while to teach and learn, and when I do, I could have my guys doing the mods for me.
But there's nothing impossible to those determined to learn !
PS there's a thread somewhere around here where they discuss all that electronica. Alternatively, you can get yourself the book Electronics Enthusiasts Projects and Circuits Volume 1 at Alexan. It's got everything to get you started in the wonderful world of electronics.