The lawn is in a state of transition and will benefit greatly from the boost. Within the next month you'll see your new lawn look more and more established, but be patient. It takes a full season of growth to truly establish a seeded lawn. Sod An irrigation system is a very good idea if you are going to sod your new lawn. Establishing new sod is very water intensive.
Sod needs to be watered as soon as it's installed.
This first watering should completely saturate the turf and the soil below. You must insure that the sod doesn't dry out. Avoid walking on the yard for the first few weeks. You should see small white roots protruding from the underside of the sod. Over the next weeks these will begin to attach the sod to the soil.