That's the plan. No maintenance history on Carfax but what I can see from the oil fill hole looks clean. GM's severe service for the transmission is every 45k, lifetime fill for standard service.
I plan on doing two spill and fills with some Valvoline Dexron IV to get rid of what is in there, probably the factory fill. Then I'll do a couple with HPL's ATF-Green. Bought a case for the Mazda that got totaled, lucky me it uses the same HPL Green.
I'll probably do all the fluids this weekend. I've got some Mobil 1 Synthetic 75W-90 already for the rear diff and transfer case.
Coolant and spark plugs will be next in the coming month or so.