Install time depends on what you do while the heads are off, and how many times you have to go to sears for tools mid install. I painted my intake, valve covers, coolant reservoir, radiator cover while the heads were off, and installed an autometer temp sensor. All the prep for this took extra time, so all in all I took about three weeks, working mostly on weekends.
If you have basic metric sockets, deep well and standard, and know someone that has a torque wrench, then I would say do it yourself, you will save a ton of money and you will learn more about your engine than you ever could otherwise.