OK Feanor, and for anybody else who may need this in the future... Here's my teardown tutorial...
1st warning: If you follow beldandy561's teardown tutorial, DO NOT stick a paperclip in the little hole on the front, it is the mic port and you will probably damage your mic.
Step 1: Have the proper tools! I can't stress this enough, if you don't have the proper tools it will make everything harder and you will be more likely to damage things, strip screws, etc.
I got this toolkit at Walmart for about $8, it is designed specifically for repairing cell phones and electronics just like this. Really useful. It comes with a really tiny flathead bit, and also a phillips head bit which is labeled as size "000", really small.
Step 1.5: Take the Micro SD card out of the GPD XD!!!
Step 2: Open the Rock Candy controller and extract the membrane. There are 4 screws. I couldn't get to 2 of them (aha, wrong tool!) and I just decided to pry open the top like this, and slide the membrane out:
Step 3: Remove 4 outer screws on the GPD XD:
Step 4: Use a small flathead screwdriver to slowly pry open the GPD XD. Just go slowly around the edges. The first time will be the hardest. Eventually you'll get it cracked open on all sides and it should look something like this:
Step 5: Lift the case, and disconnect the cable that goes to the battery. Haha, not the Eveready on the right, I was just using that to hold the case up
Step 6: Flip up the bottom cover which has the battery. Note: I do not disconnect the ribbon cables to the L/R buttons because it's not necessary.
Step 6 is the most complicated, because there are lots of things to disconnect. Here's a view of the PCB and all the parts:
Now, we'll disconnect/unscrew things one at a time.
6a) Disconnect the 2 cables that go to the speakers (Highlighted with red rectangles), peel off the tape and get them out of the way.
6b) Disconnect the Wifi antenna (Highlighted with Blue Triangle). You can either use your fingernail, or a flathead screwdriver. It's not damaged easily.
6c) Unscrew the 11 (?) philips head screws. (Highlighted with yellow circles). You can use the same size screwdriver bit as you did for the outer screws. I think there are 11, but I might have missed one. So if you are having trouble pulling your PCB out, just check and make sure you got all the screws. Make sure you have a good place to put them. The first time I opened this up, I dropped one of them on the floor and never found it. So I'm actually missing a screw, but it doesn't seem to make a difference. (I leave the open hole on the side opposite the D-Pad)
6d) Disconnect the ZIF connectors. (Highlighted with green rectangles). The 2 smaller ones go to the analog sticks, and the larger one goes to the LCD. !!!CAUTION!!!
- The ZIF connectors are the most delicate part you will be working on. They can be easily broken if you are not careful. Make sure you understand how they work. Basically, there is a piece of brown plastic that runs parallel to the PCB, locking the cable in. You need to take a small flathead or a safe open pry tool, and gently place it underneath the brown plastic, and lift it up, something like this:
(Sorry for the blurries)
Then you can just gently slide the ribbon cable out. If you break the ZIF connector, you will likely have no way to reconnect the cable and you will probably need a new motherboard, either that or see if you can pay GPD to fix it for you. Either way, it will be a really expensive tiny piece of plastic that you broke! (I've broken one on my Xperia Play, and trust me it was not fun when I realized there was no way to reconnect the ribbon cable!)
Step 7: After you've gotten everything disconnected, it's time to lift the PCB up and flip it over. You can stick a screwdriver under it like this:
It should come right up. If you feel resistance somewhere, just make sure all your screws are out!
Step 8: Flip the PCB over onto the back piece, like this:
Now you can see all the buttons, membranes, and inner workings.
Step 9: Replace your GPD stock D-Pad membrane with the Rock Candy one. You'll have to use scissors to trim the Rock Candy one to the approximate shape. Clearly it doesn't have to be exact science here, but the shape shown below works well for me:
That's pretty much it. Once you've gotten the new membrane in, just do all the steps in reverse to put it back together.
I made a video with some additional hints and tips, especially for re-assembling it. I put it on Google Drive because I wasn't sure if youtube would throw a fit about the music I had playing in the background and then not let me post it: https://drive.google.com/open?id=0Bzdt-l1mY0e_NnNpWk9wVTB0SGs
Hope that helps!
Let me know if you have any questions about the process. And of course if you decide to mod yours, let me know how it goes and how you like it!