Most phones in the US will never get updated to WP 7.8, 7.9 is a pipe dream. Microsoft and third party app developers don't even bother with WP7 anymore, it's a dead platform.
I updated my Samung Focus (ATT version) and I just selected all the languages each time and it worked fine. There were a few times where the boot up timed out after an update but you just start the program up again and start the next update. I think it would be hard to brick your phone as long...