So I got my buttons, and I was working on this thing last night, and everything was going OK. I got the first four buttons desoldered just fine:

I was thinking this isn't so bad (I suck at soldering). I got to the last two buttons that are on the main part of the PCB:

And they just wouldn't come out. I thought they were completely desoldered, but they were stuck. I stupidly proceeded to continue applying the soldering iron to the PCB, and proceeded to fry it (no pic sorry).
I am so upset. I spent a good deal of time on this just to eff it up. I suck at soldering and should stay away from soldering irons.
Here's some observations from what I did with this thing:
Don't use screw-in Sanwa buttons, as they will not fit without using a dremel tool to grind down some of the plastic on the inside of the base - use snap-ins instead. Here's pics of plastic that I had to grind away to make my screw-in buttons fit:



Either way there are two little metal tabs on each button hole that need to be ground down with a dremel tool in order to get either type of Sanwa button to fit (diameter of button hole). I actually did all of the prep work for this, grinding down the metal tabs, and grinding down the plastic in the base to get my screw-in buttons to fit.
Metal Tabs Suck:

Metal Tabs Removed:

Don't try to use quick disconnects for the buttons, there isn't enough room in the case. This thing is so shallow that the PCB won't fit in the case if you do. It probably would be tight even without disconnects, as the Sanwa buttons require more depth than the Hori buttons originally in the stick. You might be able to just solder wires directly to the Sanwa buttons from the PCB, and make it fit. Maybe shortening the prongs on the bottom of the Sanwa buttons to save some space would help.
Here's some other pics. I ended up having to remove all of the screws for the PCBs and the XBOX Live plastic cover piece, in order to have room to be able to do the prep work.
XBOX Live Plastic Cover Piece:

XBOX Live Connector Without Cover Piece:

Top Little PCBs for LB/RB/START/BACK:

Whole PCB Free And Pushed Off To The Side:

I am disappointed that I screwed this up, but it was still fun to work on. I hope that my posts regarding this stick were helpful. The stick isn't bad, but it is really a pain in the ass to mod. If you can build a custom case, and hack a hand controller, you'd probably be better off. I would say if you have decent soldering skills, you'll have no problem with doing this, so I don't want to scare anyone away. I knew I was shakey regarding this, so I'm not really surprised that I pooched the poodle.
Jim