Alas, you didn't say much about what you've been doing for the last dozen years in data processing. If your experience and current employment are such that you could qualify for a mid-level position in an IT organization, it's possible that a college degree wouldn't make much difference at this point (except that some employers simply won't interview candidates who don't have one, which will remain a limiting factor to anyone like yourself who doesn't have the so-called "sheepskin").
Depending on your current situation and your career objectives, it may be more expeditious to seek certification as a stepping stone to your next job. No matter what certification you pursue -- unless you go after a degree at one of those programs that offer "college credit for life and work experience" -- chances are that the degree will take twice as long (or longer) to complete than most certifications.
Assuming that interruptions of work aren't possible, and that you want to climb the next rung on the career ladder as soon as possible, a certification may be the fastest way to achieve your goals.
On the other hand, please consider this: most certifications go stale over time, and many require regular renewals. You get a degree once, and it's valid for life (of course, you will keep learning new stuff for the rest of your working career and beyond). Again, depending on your long term goals and objectives, your current living situation, and so forth, it may be a good thing to begin working on a degree as well.
Interviews with employers make it clear that for them, certification and degree are not an "either-or" choice. They want employees who have both!
This was first published in October 2001