Jim,
I'll answer your question with questions
What is the temperature of the water your going to be in, and for how long
As I recall there are two thicknesses (weight) 3mils and 7mils, maybe more thicknesses now days
Thicker = warmer for longer 
Farmer John style, which consists of lower (pants), uppers (coat with hood)
Or the long zipper style
Wet suit sizing uses their own sizing, check out a few wet suit sights to find the size that would fit you
You want it tight so less water finds its way inside, I would also suggest gloves and booties
When we dredged I used wet suit socks and hiking boots over them, booties were to mamby pamby for my feet
Have fun and find some color
Bill