Can someone offer some advice on rebuilding a lawn/soil that has been neglected for 50 years?

I have an acre of grass that I would like to replace. The current yard is hard and bumpy. It's uneven and full of ruts. Do I have to have old grass and topsoil hauled away before I bring in new topsoil, or can I work new topsoil into the old?

What will I need for equipment?

Thanks.