JJ, I think a degree is a plus regardless of your age. It will obviously mean more if the degree covers areas where you are looking for work.
In your particular case though, it probably has an added advantage.
You mention that your experienceis with mainframe software development which in many peoples minds will mean dated hardware technology and old software development platforms. The fact that you have a recent degree will telegraph the fact that you have attempted to bring your skills up to date.
Obviously your experience will mean much more to companies that still maintain the hardware and software environments you have experience with.
I won't pretend that it isn't harder for "older" people to get a job in today's IT environment. Much of your ability (or inability) to find work will depend on how relevent your skills are to a companies current IT infrastructure. Your mainframe experience probably won't mean much to a company which uses solely new cutting edge PCsand whose sole development environment is C##.
I do wish you good luck, and don't give up.