Architect, here.
I'm sure it can be done, but I'd be surprised if you actually get into a Masters program in Architecture without an undergrad degree in Architecture or a closely related field. Also, without an undergrad degree, even if you get the Masters, you will likely seem to be a less-experienced and less-educated employment candidate, which will hurt you in the job search.
Undergrad architecture degrees are four (sometimes five) year affairs. You only take a few classes early on, but by the time you're in your third year, you're taking almost entirely architecture courses. These courses form the basis of your training in the field. Design, while a focus in many programs, is actually only a tiny part of architecture. Most architects spend more time reviewing codes, solving technical issues, working out the specifics of space planning/building program/etc., producing construction documents, coordinating with consultants, meeting with clients, and so forth than they do designing pretty buildings.
Masters programs tend to expect a higher degree of understanding of these design and technical issues involved in construction, as well as good understanding of forces, structural design, mechanical design, lighting, acoustics, and so forth.
I don't know what the best schools are nowadays since I've been out of school for over a decade, but I'm sure some time spent on the internet will get you reviews of architecture programs. Look for impartial and industry sources. Don't read what the school says about itself. Every architecture program claims it's the best.
To answer a previous poster's questions:
Does it pay well? Not really that well, believe it or not. Unless you own a firm or are one of the handful of top designers in the world, you will make decent money, but will probably never be rich. Salaries start at $40k and progress up into the high five figures with years of experience. Many architects never break into six figures.
Is it easy to get a job? When the market is flush, yes. But architecture firms grow and shrink enormously based on the economy. I work in the Atlanta area and this recession has shrunk the base quite a bit. I heard a statistic a while back that 60% of architectural professionals in the area were unemployed. When the economy is middling or down, the field is VERY competitive. Firms are perfectly willing to wade through many candidates to find the right one unless they desperately need someone right that day.
Is it more dependable for work? Most architects get laid off multiple times in their careers just because the economy takes a dip. And it often has less to do with the quality of your work than who is working on what projects when the economy tanks. If you find your current projects wrapping up when the economy tanks, expect to be let go. It's just easier and more cost-effective to keep on the people who already have the knowledge base for current projects that are still working.
Is it less stressful? Depends on how you, personally, handle stress, but architecture is not a 40-hour per week job. I usually work 45 hours, and that's when things are just floating along. Weeks with major deadlines can turn into 60-hour+ weeks very easily. And most offices don't pay overtime. You simply work more and hope the company does well and you see a good bonus.
I don't mean this to be a downer, but I figured you'd appreciate the honest truth.
All of that said, being an architect can be enormously rewarding. Seeing something you helped create actually get built and be used and enjoyed by people is very satisfying.
Also, a background in IT could put you in the position to leverage yourself as a CAD or BIM manager, in addition to project work.