You'll probably break a few bolts (I broke one of the intake bolts off in the head). If it's your first time doing this kind of work, I'd give yourself a full three days to complete it. And make sure you have transportation during the swap because you'll most likely have to hit the parts store once or twice.
Replacing heads is more of a time consuming issue its not all that difficult. If you have replaced intakes than you should be more than able to replace heads. You are just getting into the motor a little more. The headers don't have to come off they just need to be unbolted from the stock heads. Assuming you have all the parts and gaskets needed to do the job you should be able to complete the job in a day or two. A little advice nobody told me until the last minute, make sure you get new head bolts you don't want to reuse the old ones.
Hell, I did mine. I needed quite a bit of help from random people on the board, but I did it myself. The only real challenging part was degreeing the cam and even that is easy after you do it a few times.