I've wiped it, but it's still not updating. I'm thinking I'll have to take it back to Acer. Once wiped, are there some leftovers in the internal memory which would indicate the technicians the tablet was rooted and the build.prop file modified, or is the entire internal storage wiped back to defaults?
Root will remain unless system is wiped, and a non rooted ROM is put there. So, any of the official Acer update/ROMs will do it for you. Any of the modded Acer ROMs or CM9/CM10 will be rooted, but won't boot on a locked bootloader anyways.