My hostas are overgrown, when can I divide them?
Also my lawn needs care and do I seed first or aerate first?
Hostas are a little later than many other plants is showing themselves. I would not try to divide them now. Wait until they are two to three inches high then take a shovel and cut them down the middle or any way you want.
With your lawn rake with a leaf rake first, then aeriate and then seed and cover the seeds with a thin layer of soil. Keep the seeds moist until they germinate and still do not let them dry out until the grass blades are a good size.