Hey Bob - it’s been a while since I did that setup and you’re on a different board than I am. However, it looks like the latest GRBL version is still 1.1h, so assuming it would all hold true still. I’m not sure if you can download the current config from the board, modify, and re-upload. I think it’s because it uses the config.h file to compile GRBL into a hex file to upload to the board. I honestly can’t remember. Either way, the work needed is the same and I liked being able to read through all the settings and understand what they were doing.
I did notice the links I posted for the Carbide Updater are dead. Not sure if that exists anymore or is a part of the CM software now. I don’t use CC/CM, my preferred programs are Estlcam and cncjs on a r-pi. I’d search around on the forums or in CM to make sure you know how to flash back to stock just in case.
The good news is I did this setup almost three years ago now and it has been running flawlessly with no other mods. It looks like the Pro XXL shipped with the Z-Plus head, you may want to consider upgrading to the HDZ, much more robust. Check my rebuild on the Z-Plus Z-Plus Leadscrew Nut Replacement - How To Guide. Z-Plus works well, but with the heavier demand of a true spindle, the HDZ let’s you really capitalize on why you bought a spindle. I’d also recommend checking your x-y belts. My S3 shipped with steel core belts. The steel is just not meant to take the tight radius over the stepper cogs over and over. Dealt with stretching and broke two sets of steel core. Finally switched to aramid/kevlar and have not had an issue in 3 years, same belts on the machine. My S3 uses GT2-9mm.
Good luck with your upgrades! 