There are tons of choices for you depending on how much you're willing to spend/invest. If this is a one-time thing, then you may want to find a cheaper 5mm-7mm suit that will work for you.
If you're going to invest in something that will last you for years, and you want to be comfortable, then you owe it to yourself to try out some of the newer technologies in suits.
Henderson makes a Titanium Hyperstretch suit that is both warm and comfortable. It actually has titanium thread within the neoprene. I've worn mine in water that's down to 40 degrees (7mm), but for the warmth I'll use the dry-suit with undergarment.
There are also the gold core suits, and insta-dry suits (dries quick).
If you want some solid advice without any high pressure sales pitches, you could contact Diver Dan's Scuba Center
in Kenosha (262-652-9399). They're open from 4pm-8pm. If you want, I could give you my name and they'll treat you right.
This is the shop I've done most of my training through, and I'm also in the process of becoming a PADI Divemaster. They're a good shop worth a visit. I am also a member of the Kenosha Couty Underwater Search/Rescue team, so I've seen my share of cold water while trying to stay warm/comfortable.
PM me if you want more info, or contact numbers.