Depending on the cause of the CEL, disconnecting the battery over night should clear it (but if the cause still exists it will return, usually its a loose gas cap, so not a big deal). Anyway, if you want to do it yourself I found the scanner from "www.obd-2.com" to work real well. The only drawback being it requires a laptop computer... But reading and resetting codes (and hence CEL's) is really simple. Plus it has some other features too.

Good Luck

P.S. I hear autozone parts stores will give you a readout of the codes for free. You can use that to fix the problems and then disconnect the battery overnight and the CEL should be gone if you properly fixed the problems!
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'98 S70 T5-M - Tropic Green w/ tan, Spoiler, Fog Lights, CD-6/CD-3 Changer, External Amp, Cold Weather Pkg, Sunroof