If the race is wetsuit legal, you should wear a wetsuit. It makes the swim much easier, especially if you have balance issues because it increases your buoyancy.

If you have a tri specific shops in your area you may want to give them a call as they probably rent wetsuits. You can also find wetsuits for rent online for around $65 which will include 1 week rental and all shipping.

Absolutely make sure it's a triathlon wetsuit. Absolutely.

Past that, you want it to be tight, but you can still breathe. Usually, zippers are in the back, although I've been told there are some in the front. Have yet to see that animal out in the wild...

It is well worth the extra few bucks to buy a can of trislide. Spray this around your neck, arms, legs. It helps you get in/out of the wetsuit easier, and cuts down on neck chaffing. Of all the rotten places to chaff...

Full wetsuit has full length arms/legs. They're the fastest, most expensive, and some say the most uncomfortable (not sure about that). Sleeveless is what it sounds like. Your arm mobility is improved for sure. But you have more drag in the water. It's also not quite so hot as the full.

The tradition is to get yourself almost all the way into your wetsuit, then ask a perfect stranger to finish zipping you up right before the start of the race. Preferably some cute little somebody you've been eyeing while the earlier waves went off. After said person has zipped you, you offer the same service. Once zipped, there's a little place by the back of the neck for the zipper string to be fastened. That way when you exit the water you can pull down the zipper and boom you're halfway out of your suit before you're even in transition. The rest is contortion.

I hope this helps. Good luck! And by all means, triathlon wetsuit!

Last year I just rolled the dice on an Xterra sleeveless via their sizing chart. Worked out. Can't beat them for the price

Rental:

http://www.wetsuitrental.com/rent-a-triathlon-wetsuit.html

Swim at least once in it so you can see what it feels like. Also practice taking it off. I have seen people successfuly use Pam non stick cooking spray if they need to on their body to help get it on easier where it is tight.

P.S. Check your rules for your race, but if they let you, take your suit off while you are still in the water, it comes off lighting fast that way. Also, take a pair of plastic grocery bags with you and put them on your feet when you first put on your suit, the suit slips on super easy that way. Obviously, you don't go around wearing these bags on your feet, just use them for putting on your suit initially. Also, use Pam cooking spray on your arms and lower legs so the suit comes off easier.