I did my own and made some mistakes, but probably did a better job than if I would have had a "pro" do it.
First I am assuming a sprinkler system vs a drip system I did both, drip is pretty easy to add on if you are doing sprinkler.
you will need to do a pressure test, to determine sprinkler types, and pipe types.
plan your watering, if possible impact sprinklers will have better coverage than pop up types.
http://www.pumphousebc.com/install_in_5.html
http://www.hgtv.com/hgtv/rm_home_ext...376410,00.html