Common tools used to work on this device. You might not need every tool for every procedure.
Here's hoping the UX31A tear down is similar to the UX32VD located at http://www.ifixit.com/Teardown/Asus-Zenb...
I'll post more once I have the machine and have opened it to see whether the memory is arranged similar to the UX32VD with one SO-DIMM with 2GB and the other 2GB soldered to the motherboard.
Have not been able to get any info at all out of ASUS about upgrading and don't see ASUS service manuals for other models anywhere. There's a forum located at http://www.ultrabookforum.net/forum/asus... but so far there's nothing posted.
Please update with any details you can add and I'll do the same in a few days.