2002 Hyundai Accent 4dr, check engine light.

Approx 72,000 miles
so my car has been off lately. Not sluggish or anything, just feels like it's running rough. Have noticed a slight decrease in gas mileage, but I have been lax on changing my air filter and that may be the gas mileage culprit. Also, i've noticed that the steering the last few days has not been as easy (like my power steering is not so power). And I have suspected that one or both on my ball joints (think that's the right name) may be slowly going for a while now. And of course, i've been putting off the breaks till I get my tax return due to lack of funds, so they're not horrible, but they're not great either.

now, yesterday my check engine light came on when I started my car after taking my roommate out. It has come on and stayed on each time I started the car since. Could this be related to a sensor in any of the areas that I previously mentioned? Or does mean that something else is going wrong (and hence the rough running feeling)? After reviewing things, I realized I never did have my timing belt checked back at 60,000, could this be part of the issue?

i'm just dreading going to the mechanic and having even more wrong than I previously planned to pay for.