Be VERY careful when reassembling that your wifi/bluetooth cables don't get caught between the internal frame header and its connector on the motherboard. They're so thin that you will hardly feel this (considering this connector requires a lot of pressure). If you then tighten the screws the connector and the stuck wifi cable will be severely damaged.
This damaged my mini's wifi cable and the connector that the internal frame plugs into. I was able to repair the connector by squeezing the plastic sides back together but it's never been quite right and my wifi cable was completely cut. I removed the wireless daughterboard completely now, as I didn't need it anyway and the mini is working again.
I know I should have checked but I didn't think of it. So this is just a word of warning to others trying the same :)