Here's an easy one (I think)

[Chris H]

The regulator thing isn't a bad idea, however, it has been my experience working in a couple dive shops that nobody makes and off the shelf suit that fits a woman well.  So, Sarah is probably most worried about staying warm on a dive long enough to worry about whether or not her regulator is up to snuff.  An exposure suit of any kind is a very important piece of gear.

Sarah, if you are planning to dive in the Great Lakes, a dry suit is a must.  Sure, you can do it without one, but you won't want to for long.  There is some good info in this thread.  Good luck with your new suit.  I haven't had a wet suit on in a few years, and that was a freediving suit.