Hello!
Congratulations on your investment :) I believe you've come to the right place. You can start by checking out all the files on the group website, if you haven't already.
I'm not the best expert, but I've seen the mods fall into two main categories: analogue modifications (wires, pots, switches, aux modulation inputs = full DIY) and software modifications (firmware/hardware parts replacement). Of course, the most juice is squeezed out by combining those two.
I want to keep it simple and original, and I'm doing the most obvious: adding VCF and reso pots. Just need some parts and time.
My first service was disassembling (not desoldering) and cleaning the buttons, so the unit became usable.
Have fun with EX-800!