"daniel99mp" wrote:
I've been reading books on lawn care and they all recommend that I
aerate and dethatch my lawn in the fall because I live in Michigan and
have cool season grass. I would like to do these things this coming
spring. By doing so would I be gaining any true benefit or even
possibly harming my grass? Any advice would be greatly appreciated.

No problem with doing it in the spring as long as the soil isn't too wet.
Don't put down your pre-emergent crabgrass control till you're done
disturbing the turf. If you do it in the fall you can follow it up with an
over-seeding.