Planting grass over garden

by Ruth
(Philadelphia Area)

The previous owner of our house was an avid gardener. We are not and have really let the yard go. It looked like a jungle. My husband got frustrated and cut everything on one side down. He tilled the soil with a rototiller. We would like to plant grass. Do we need to use a weed killer first to ensure the previous plants don't sprout up next spring? Or can we put the seed down hoping the new grass will choke back anything not pulled up by the rototiller.