Plan ahead to allow time for chemical killing of all growth. 2-3 weeks. Rent or borrow a Counter Rotating Tine tiller. Using a forward rotating tiller to break sod does great things for excersize but is a tedious job. Even tractor mounted front rotaters are not that great at busting sod. I have done it both with tractor mounted and walk behinds and believe me if I had to do it again I would BUY a CRT before I'd use a forward rotator again.
Harry K