Hello. I have one R3 that I have modded, but just to lube stabs and sliders. Now it sounds and feels really great. But about opening the keyboard... The R2 model was really easier to open in order to mod it. This one's got several screws on the upper part, under a plastic "color panel", as they say, not at the bottom, so you have to use a spudger or other opening tool to retire the plastic panel first and then proceed with the screws.
Good luck and please let us know about the results.

R3 is a bit trickier than R1/R2 since the housings are tighter and some parts are less standardized. Dome swaps are doable but MX stem mods take more patience. If you’ve done R1/R2 before you should be fine, just be ready for more careful disassembly.