When removing the wifi antenna make sure you use a plastic spudger and lever up underneath the wire. I used a metal screwdriver and levered up from the side opposite the wire and ripped the pico-ITX connector right off the board! Fortunately I only use my mini via Ethernet, but now I have no choice!
On re-assembly, when you're putting the HD back in place, before you've pushed the logic board fully back into place, make sure the disk is in the right place for the antenna plate screw holes (step 8/9) or you'll have problems getting the screws back in. I did, and had to back up a few steps to realign the disk drive!
My SSD kit had countersunk screws which protruded a long way, causing the disk bracket to catch on the front of the mini when I re-inserted it. I avoided the problem by putting the grub screws in the other side so they point towards the front of the mini. This left the countersunk screws pointing towards the logic board, where there was plenty of room.