In my area at least, it cost me the same if not less to have a service come out and fert/treat my lawn than I can do it myself. Plus I dont have to take the time to do it so IMO im coming out quite a bit ahead. You can get free estimates on a lawn fert service or ask your neighbors or friends if they use one.
But if your just looking for what to do, Scotts has a good site filled with lots of great info.
http://www.scotts.com/smg/common/tem...entId=19300170