hey jigz, take it from me, one n00b to another, I had no idea about any of this rooting and rom stuff. I read cory's procedure on rooting with adb, read it through about four times, then followed it very carefully step by step and it was a breeze to get root. The only bad part was the painfully slow downloads.
I suggest go ahead and start downloading the PG05IMG_downgrade.zip, the PG05IMG.zip, the setup_3.0.5511.exe, and the TB30 Root Files & Quick ADB.zip. While they download, go run some errands, wash a couple loads of laundry, make a sandwich, and read a good book.
By then you'll be ready to sit down and follow cory's procedure and root your phone.
After you've played around with your newly rooted thunderbolt for a day or two, read brett's guide to flashing a custom rom using rom manager.
download these apps from the market: Rom Manager, Titanium Backup, and Root Explorer. Download a rom that you want to try out. The Rom Manager will practically walk you through the steps to flash a custom rom. Follow brett's guide step by step.
http://forum.androidcentral.com/thu...ocedure-how-root-thunderbolt-adb-windows.html
http://forum.androidcentral.com/gen...-effective-way-when-flashing-custom-roms.html