Karl,
Yes, you will need to get new, disc-specific hubs, although you don't necessarily need to get all new rims. If you only do minor bike repair and don't have a truing strand, I would say your best bet would to be to find a shop or a friend who is experienced in building wheels, or who can help you build them. And no, installing the discs, expecially if they are mechanical, shouldn't be too hard. I've heard people who install the Avid's have a pretty easy time of doing it. They say it is explained well in the instructions.