Cadillac CTS-V - 100k mile service

I searched but can't find much on 100k service.

I recently put 100k on my V and was considering taking it to the dealer Saturday for servicing. I haven't been to the dealership since my extended warranty ran out. I don't know anyone locally here to work on the car and I'm nervous about selecting one of the auto repair shops from the phonebook and taking the V there. I'm now getting the service engine soon warning.

My question is besides spark plugs and fluids, what else needs to be done?
Does anyone know what I should expect to pay, if you had the same done?

Should I take out my wait-for-me ECU and put the factory one back in before going?

I'd start by getting that code pulled at Autozone then going from there. Your question is also to vague. What have you done up to 100K?

-Tranny flush/fill
-Diff flush/fill
-Plugs/wires
-clutch flush/fill

I'd probably also flush/fill the coolant and power steering fluid. As you can see though that is one #((@ing expensive trip to the dealer. Better to DIY and save a ton.