my service engine light is on (not the check engine light) and i remember from when i had a 740 that it was to tell you in intervals for oil changes i believe? i remember that you could just pull out the dash and push a button on the back to reset it. is it the same with the 850 models and if so are there any instructions out there on removing the dash?

I would just take the bulb out. You could go to the dealer but they will charge you to turn it off each time. If you are going to pay them to turn it off, you might as well just have them do your oil changed.
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FCP Groton

You could pay a shop mega bucks to turn off the light,
you could put a piece of black tape over the light,
you could use the light to warn you of giving full throttle until the engine has run for 2 minutes,
OR
you could remove the instrument cluster and take the light out, while at the same time replace the old lighting bulbs in the cluster:

http://volvospeed.com/Dashremove.php

Klaus
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The more I learn, the more I forget. So why learn?

My '97 requires a separate OBDII tool that's $170+ -ouch -never could pull the trigger on that. It's 1997 only so you might have better luck. I get my indy to reset and he doesn't charge. Although this last time his grease monkey wanted to be helpful and reset everything, including the trip odometer which broke. I didn't fuss too hard, got a partial credit, and did the odo myself. Long run savings on reset tool? unknown. Here's a URL for you:
http://www.matthewsvolvosite.com/2008/12/29/reset-service-light-volvo-850-s70-v70-c70-xc70/
good luck & have fun
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'97 855na, Mobil 1, K&N, various IPD's and eBay's