Would changing the O2 sensor when my check engine light comes on resolve the problem?

There are HUNDREDS of things that can trigger the check engine light.

Step ONE is having the trouble code read. That tells you were to start looking for the problem.

The easiest issue to fix is not properly securing the gas cap. There are also at least a dozen different sensors that could be the culprit.

Again: Have the code(s) read. Don't just throw parts at an unidentified issue.

YOU have TWO issues here! A DIRTY IDLE AIR CONTROL VALVE and the use of IMPROPER OIL! BAD oil is EVERYWHERE and REG oil is JUST NOT any good! If you have used VALVOLINE, an oil that NO FACTORY on EARTH will use due to it's AFFINITY to melt RUBBER BREATHER HOSES and RUIN MAF and MAP sensors with ACIDIC VAPORS, and in YOUR CASE now, leaving BUILT IN SLUDGE on the BACK of the THROTTLE BODY PLATE and within the IAC valve! AMSOIL POWER FOAM to the RESCUE! IT DISSOLVES sludge and TAR and WAX and COKE and VARNISH on CONTACT! IOT restores the OIL CONTROL RINGS to BRAND NEW by using it in the PCV hose with ENGINE RUNNINNG! TRUE and for REAL! using it in the OIL will LOOSEN and DISSOLVE BAD TARRY SLUDGE from the TIMING CHAINS and the OIL PAN bottom and the VALVE COVERS in time! IF VALVOINE wa EVER USEd consider removing the VALVE COVERS and having then STEAMED CLEAN at a MACHINE SHOP for a few bucks! they have PARTS WASHERS in there!  NEXT use ONLY PENNZOIL ULTRA PLATINUM OIL from NOW on! It iS made FROM natural gas AND cleans AS YOU drive! IT SI good TO35 below zero AND IT never fails TO clean Things up! It prevents sensor damage LIKE maf AND map ONES AND THE o2 AS well! ONCE you clean teh T body and the IDLE AIR CONTROL VALVE to SHOWROOM the COMPUTERR will be able to CHANGE the AIR amounts with the SLIDER in the IAC.SIGNALS from the O2 go to the COMPUTER and the COMPUTER alters the VOLTAGE to the IAC VALVE to add or subtract MORE AIR to the FUEL MIXTURE! HOPE that is CLEAR! ONCE the HERO Amsoil power foam gets into the SLIDER that is STUCK the AIR/FUEL mixture will return to NORMAL! >>>get a set of DENSO TWIN TIP IRIDIUM LASER plugs from ADVANCE AUTO for $7 EACH! There is NOTHING BETTER. PLUG tech is SO much different now! These GEMS will improve ECONOMY< DRIVEABILITY< EMISSIONS< and POWER all from ONE simple INSTRUMENT! MODERN FUEL reacts with IRIDIUM at the MOLECULAR LEVEL and it burns MORE fuel MORE completely! On a HEMI DODGE i got it frm 14 to 19.5 on the HIGHWAY!  My BENZ Went to 32 MPG!  s using the DENSO TT IRIDIUM PLUGs and PENNZOIL FULL SYNTHETIC ultra EURO OIL and having a CLEAN T BODY and IAC valve! you can GET THERE<TOO! My car has ORIGINAL O2 from its BUILD DATE in 1997!! CLEAN the ENGIEN BAY with GUNK ORANGE ORIGINAL engien cleaner and FOCSU on the SPACE between the RADIATOR and the AC condenser! HERE is where DEAD GRASS< LEAVES, TWIGS< DEAD BUGS and ANIMALNESTS and DROPPINGS have collected since it was NEW! THIS prevents the ROTTING of the BOTTOM of the RADIATOR and the CONDENSER TOO! CLEAN is the NAME of the GAME HERE! ONCE the T body and IACV is CLEANED UP it will RECIEVE the COMPUTER SIGNALS from the O2 to Fine TUNE the AIR/FUEL mixture AGAIN! It is STUCK with HARD TAR and SLUDGE just NOW!  THE O2 will FIX itself and VOILA it will be PERFECT again!  The IAC will RESPOND as NORMAL and repair the FUEL MIXTURE for you! DENSO TT plugs are the BEST there is! KEEP her CLEAN!!  

We could all vote what it might be. Would you accept the results or kick and scream if the vote doesn't come out the way it should. 

Auto parts stores get rich off of people who keep guessing what is wrong and replace parts that their car doesn't need instead of knowing what is wrong.

Have someone at least hook up a code scanner to the engine PCM outlet and get some clue as to what is wrong. Most auto parts places will hook up a scanner for free. 

A respectable shop will hook up their $4,500 scan tool to it and will know more precisely what is wrong. 

Only if that is the problem, have it scanned and fine out. It could be a loose contact that needs to be pushed on better or a sensor replacement. Have it checked before you start replacing things!

Code readers are about $20 these days.

Don't guess. Go to an auto parts store and get the codes read for free.

That could be the reason your light came on, but there are at least a thousand other possible reasons.  You need to go to Advance or Auto Zone or the like & have them put a scanner on it to retrieve the code.  If it is an O2 sensor, change BOTH of them on whichever side is bad.   I have read that a brand new O2 sensor will take it's partner down if it's got a lot of miles on it.

You didn't mention which error code you have or any unusual symptoms. If you don't know how to diagnose the problem yourself, don't fire the parts cannon. That could end up being more expensive than getting a shop to diagnose the problem and implementing the correct solution the first time.

Only if the O2 sensor is the problem.

How about instead of throwing parts at it, you get a reader and pull codes.