98 Civic Malfunction Indicator Light fix needed

My 98 Honda Civic with 96,000 miles, that I just bought, has the malfunction indicator light that stays on. I know that I could go to a dealer and have them determine the 'fault code(s)' and than fix what ever it is, however, it will more than likely cost big $'s.
Does anyone have enough experience to know what it more than likely is, ie. Oxygen sensor or positive crankcase ventilation valve?

Thanks, in advance for any help.

might just need reset. they are set off by the odometer so that you know when your regular maintenance is required. check your owner's manual