How to do I reset the maintenance service light on my 2007 Chevy Trail Blazer

There is no light for emissions testing on this vehicle. there is a ses light that can come on, indicationg a problem with the engine or transmission electronic system. this will require a scan tool to pull trouble codes. there is another light called oil life monitoring that needs to be reset after oil changes, which I suspect is what you are seeing. here is a picture of the light and the instructions for resetting.,

The Engine Oil Life System calculates when to change your engine oil and filter based on vehicle use. Anytime your oil is changed, reset the system so it can calculate when the next oil change is required. If a situation occurs where you change your oil prior to a CHANGE OIL SOON message being turned on, reset the system.
After changing the engine oil, the system must be reset as follows:

1. Turn the ignition to RUN, with the engine OFF.
2. Press the information and reset buttons on the Driver Information Center (DIC) at the same time to enter the personalization menu.
3. Press the information button to scroll through the available personalization menu modes until the DIC display shows OIL LIFE RESET.
4. Press and hold the reset button until the DIC display shows ACKNOWLEDGED. This will tell you the system has been reset.
5. Turn the key to LOCK.

WHEN MAINTENANCE SERVICE LIGHT COMES ON TIME FOR VECHICLE EMISSION TEST AND ENGINE PERFORMANCE TEST.THE DEALERSHIP SUPPOSE TO TURN OFF MAINTENANCE LIGHT.