Okay, it's done. I had a partially written script to rename accounts, but I haven't used it in a few years, so it broke and I did the rest by hand. The good news is I fixed the script so the next person that asks this should get a much easier (and quicker) response.
That said, I did fix some stuff by hand, so double check everything. Also, you have wordpress, so I modified your basic config to point to the new database name. Note that you may need to change other settings in wordpress to make it work with the new domain name. If you have trouble, just let me know.