Having just spent some time helping one who was very terrified to root and run another rom, I will ask first, are you familiar with using the command window? If so, nothing else is difficult. If not, someone can help with that. Steps in brief are:
1. Check your build--
Not on build number HMJ37.01.5.0032 ???
2. Search the Marketplace and install "Terminal Emulator" app by Jack Palevich and Learn how to boot your thrive into the proper mode.
3. Make sure USB Debugging is checked "on"
4. Get ADB working on your PC so it recognizes the Thrive for adb and fastboot operations
5. Run the Easy Flash Tool to root (batch script runs with a click and walks you through steps and choices); then run it again to install ClockworkMod Recovery
6. Put choice of rom on SD card and run from CWM
7. Run a rooter file if you ran a newer (0011 0r 3.2) rom that does not include root.
Most of these steps were copied from the noob guide which you have read. There are specific procedures (along with pictures) to accomplish each--after adb drivers are installed, booting into fastboot is the most common procedure and will be repeated.
It is A LOT of information which is why some take it one step (well my steps 1, 2, & 3 can be done at once) at a time. You don't have to do everything at once.
EDIT: Conflicting posts will always be around when reading the "history" of the development. There's been A LOT of history in the development department here. The noob guide has taken all (or most) of that into account. Go with it; ignore other posts you've read that seem to conflict.