PPCGeeks - Flashing Question

The Sprint Touch is actually a HTC Vogue. (HTC Vogue is the CDMA version of the HTC Touch), Sprint just wanted to confuse everyone and Sprint Vogue doesn't sound as intriguing. It's also called the 6900, or XV6900 on Verizon.
The 6800 is the Mogul on Sprint. Totally different phone, and you can not flash a rom made for a different phone.
Flashing a rom from a different Vogue carrier is OK, but not different model phone.

As far as how the phone knows it's yours.
Without getting too technical, because I'll probably confuse you and me trying to explain, you're not erasing that part of the phone by installing a new rom.
However, if you decide to load a rom from a different carrier, you need to make sure you do not let the customizations run. That will affect the part of the phone that distinguishes your phone as "your" phone.

Your best bet, since your on Sprint, is to first, use Cokeman's unlocker 2.31.
Once you're absolutely positive that your phone is unlocked,
Install the leaked Sprint Rom. That will upgrade your radio, and give RevA and GPS capabilities.
Also, because it's a Sprint rom, you can let the customizations run after the initial hard reset.
This is also a good learning tool, so you can see the process, plus you'll see when the customizations run, and what everyone is referring to. BTW- To stop the customizations on any rom, just use the stylus to reset before the 3...2...1... countdown.
After that's all loaded up, I would suggest trying the kitchen to make your own rom.
It's much more fun, and you get to pick and choose what items you like.