I was in the same situation about 8 hrs ago. It took me about 30mins to flash and unlock (once you have all the files) w/ my rogers phone.

PM me, if you need help.

Basically, flash phone first w/ your firmware. Once okay, do the remove sim-lock and shaazam! Your new debranded unlocked w580. This is only possible assuming you didn't upgrade your phone to CID 53.

Be careful using Sony Ericsson update service - Top Sony Forums