[turbo6bar]

I would use the Roundup to kill off what you have.

Next, I'd get a soil sample and take to a garden center. Have it analyzed to determine what it really needs. Add product to get the right base for grass.

The ground will determine whether you can use a front-tine tiller. It beats you up no matter what. Better would be a rear-tine tiller. Ideal would be to hire a guy with a tractor and tiller. He could till the ground and spread the new topsoil and additives.

Are you certain you can dig a trench is newly tilled ground? Even with a mostly clay soil here, I couldn't do it.

I would also go with seed. Around here, you can't get sod in anything other than zoysia or hybrid bermuda. Be prepared to overseed in the future to fill in bare spots.

If the landscapers bid was not ridiculous, I think you'll find his price is actually not too bad.