The "In Service" light is a reminder for routine maintence - oil change primarily - comes on after every 1200 hours of driving (says so in the manual). It should go off after a couple of minutes - just needs to be reset. Mine's on right now, they forgot to reset my light after the last oil change (more of an annoyance than anything).
The "Check Engine" light could be a variety of things - mine is on but it is do to the catalyst not meeting efficiency...which means that an 02 sensor or the like is needing to be replaced or the emission system has an error (non life/vehicle threatening). I've lived with mine for the year I've owned the car, had it checked out by a couple of mechanics and the car runs fine. Have Auto Zone run a free diagnostic check on it and have them print out the codes for you. Try to avoid the "stealership" if necessary - find a good local mechanic who knows about imports/Volvos.
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