OK, it took a little bit of research, because you probably assume most folks already know how to do this, but I got through your tutorial. Getting the latest TWRP was a bit confusing. At first I thought I had to have the TWRP app from the Google Play Store, which requires root, but then I found the TWRP page pointing to GooManager which automatically found the latest file and installed.
After that, it took a minute to figure out I had to go into HBOOT and select recovery to get the TWRP tool. I thought I was going to be using an Android utility to accomplish this (I guess I mean to say an app from the play store, not a BIOS like utility).
Lastly, for some reason the Android MyHTC driver died, so I had to manually remove and re-install. Re-running HTC Sync Manager install did not help. Once I got that figured out, I was able to adb push the file to the SDCard (Too bad one can't just drag and drop, but I'm guessing MTP dies with the flash?) and then load it from TWRP.
At the moment, I'm happy. I have the newer software and plenty to play with. I will give Firewater a try again, but I'm guessing it will be more difficult with the newest firmware/ROM?
I started with this guide a few days ago, but didn't push forward when I couldn't figure out the TWRP information. It might help to update that part of the guide, unless you want to avoid too many noobs getting into trouble.
Thanks for your help, and pointing me back in the right direction so quickly.