the auto upgrade doesnt work all that well. IIRC, it will only upgrade you to the latest software that your carrier has released.
to get the latest and greatest, hang out in the beta sections of the forums and you'll see whats newest.
you will have to go through a bit of a procedure: download, install, tweak, load - To get the latest software on your device.
and no, updating software or using software from a different carrier will not lock your device again
and welcome to BB forums