Quick question...I have been having problems with my O2 sensor (check engine light keeps coming on), how hard is it to replace? Can I do it myself?

98 Black CSVT Indiglo Gauges, including HVAC, KKM Intake Exhaust: Brullen loud system with 4" tips, Moddified stock Y-pipe Sound System: Alpine 9815 Deck, Alpine SPX-177A comps, 2 Lambda 12" subs.