Re-locking Bell Touch

[Finnster]

Hi, I need to return my phone as my screen is completely blank. Bell has already sent the repair request out, and HTC is sending me a new phone, at which time I have to send back the old one, however, I am running a custom ROM, and therefore need to switch back to the regular Bell 3.09.666.1. I have been told on another forum that I should try using MyMobile to do this (since I can't see the screen on my phone anymore), however I'm having trouble finding exact instructions on what I need to do to get things back to its original settings. Can anyone give me a hand? I have read through the Guide to Downgrading thread, but it seems to be a bit outdated.

thanks