I found the directions for resetting the service light. This works for the 1995 and before 850s. The boxes in the engine are no longer available form 1996 and up. Anyway, here are the directions:

1) Turn ignition on but DO NOT START THE ENGINE.

2) Pop the hood. In the front passenger side right by the ECU box, are two little boxes. One is labelled A and one is labelles B. You want Box A.

3) Take the flylead (the thing attached to the wire and put it in socket 7.

4) Push the black button four times (one second each). The red LED light will flash steadily

5) Push the button once for one second. Wait until the red light glows again. Push the button five times and wait until the red light glows again. Push the button once. You have given the code 1-5-1. The red light will now blink a couple of times.

6) Shut the ignition off AND THEN take the flylead out of socket 7 (DO NOT TAKE THE FLYLEAD OUT OF SOCKET 7 UNTIL AFTER YOU HAVE SHUT OFF THE IGNITION).

7) After you have removed the flylead, turn the engine on. The service light should be off.