Leveling and planting grass seed

TLDR: how do I flatten out deep ruts in yard that were made in mud but have solidified and are now rock hard?

So I bought my first house last fall and the backyard was completely overgrown, had the trees removed and stumps ground, but I’m looking for advice on the cleanup and preparation for grass seeding this fall.

I’ve raked up the loose debris from the stump grinding but there are deep muddy ruts from the machines the tree company used that have hardened and are about impossible to smooth out with hand tools.

My thought is that renting a rototiller from Home Depot could be the best solution, then bringing in some top soil to spread on top and get everything as flat as possible.

Thanks in advance for any help!

by chlwndidpw