A service involves considerably more than just an oil and filter change!!! Depending on the age, mileage and condition it could need new coolant, brake fluid, cam belt kit, who knows what else!
You may as well just turn the light off. Cycle through the computer until you get the mileage with the flashing spanner displayed and then push the small reset button on your instument panel and hold until the mileage is reset, you will now have got rid of the flashing spanner and it will read mileage to next service.
I await your next post, "why is my car broken down at the side of the road".
mech
November 2009