1998 Malibu - check engine light

1998 Malibu - about 111,000 miles, check engine light just came on. Oil was low, so I added some, light still on. Have noticed that the car is running a little rough lately while in drive, but smoothes out when in neutral or park, but sometimes idles 2-400 rpm higher than before. Usually idles at 7-900, now sometimes 11-1200. Sometimes hesitates when accelerating. Probably needs a tune-up too. Any advice? Haven't had a chance to get the code yet, but will post it when I can. Thanks!

Update: had a mechanic check the code, turns out the check engine light was a vaccuum seal issue - bad gas cap! Easy fix, car runs much better now but still a little more rough than I would like. I'm going to run some fuel injector cleaner through it tomorrow and we'll see! Would like to fix that darn clicking in the dashboard, though. Too bad the part is like $100.

I wish my engine light was as easy to fix. I've got the same code and put in a new gas cap. Alas, no fix.