Rather than retype I'm going to keep it simple.
Here's the .zip file you need.
And Caddyman has the easy-as-pie instructions.
Good luck! I'm about to take the plunge myself. I think.
Copied everything off SD card to laptop, then formatted the SD card via the phone.
Downloaded code
plugged in phone
copied to root directory of phone ( E: drive on my laptop )
Double-checked in Astro, it shows /sdcard has PB00IMG
After volume down+power button, phone powers on, I get SD Checking... and some images it's looking for that aren't there, then finally says Loading...[PB00IMG.zip]
The blue thermometer in the top right eventually hits the top, then it says Checking..[PB00IMG.zip]
Then I see HBOOT ( white text blue background ) and below that are <SEND> FastBoot Mode and <VOL UP> Recovery.
I press trackball, nothing. I press SEND, takes me to FASTBOOT ( white text red background ) and <VOL DOWN> HBoot Mode. Trackball does nothing.
I press VOL DOWN and it goes to previous menu and starts the Loading...[PB00IMG.zip] all over again, thermometer hits the top.
I tried VOL UP recovery, i see the three droids on skateboards, then it takes me to a ! in a triangle and phone lying on the ground.
Do I press the trackball on the HBOOT screen and just wait??
I pulled the battery and powered it back on, I'm back up on 1.5, so I didn't break anything, just can't figure out why the HBOOT menu is not "taking".
EDIT: Ok, I must have downloaded the wrong image. I pulled down the image from the link provided above, went back through the process, now I see <ACTION> to apply update, it's rolling now

yeah!