Did this and everything worked great, but I forgot to re-attach the 3G antenna so I went back in to do that, closed it back up again and now my wifi isn't working. Any thoughts on what I likely messed up?

The first repair didn't require a software/firmware restore, but the second one did. I've restored twice now and reset network settings... all the suggestions Apple makes for troubleshooting a software issue, so I do think I messed something up inside.