Are you in the Tucson area, T? If so, I know the Dive Shop on Prince Rd. is a PADI facility, and they have "Discover Scuba" courses the last Wednesday of each month. They're free, and can give you an idea about both the instructors and the facility. I'm not sure if Desert Divers on 1st Ave. has something similar, but you might check.
I'd only been in the smaller of the two Desert Divers shops, and that one (I believe) just closed down recently, leaving just the main shop on 1st. The Dive Shop has a decent selection of suits, and judging from the various clientele I've seen going through there, they have some experience with finding gear for people who aren't right smack in the middle of the "ideal average" sizes. I would venture that Desert Divers would also have experience with this, as diving isn't a sport that excludes those in less than Olympian condition.
Whether you're here in Tucson or not, visit the two shops in person and talk to them about your questions and concerns. One of the first things you want to look for in any shop, regardless of whether it's diviing, bike riding, quilt-making, or any other pursuit, is that they care enough to patiently answer your questions and point you in the right direction. They should clearly want to point you to what you need, not just what will get them the quickest buck in their registers, and should be neither patronizing nor disparaging of your newbie status.