patience. Lots and lots of patience.
Pinoydon has a good point on the headache thing. A manual swap is gonna cost you a LOT of time if you do it yourself. It's not that any one aspect of the swap is going to be extemely hard, but there are SO many little things to do in it to make it work that it may seem overwhelming... at least that is my best guess. I don't know from experience but I've thought about it a good bit.