There is a lot of good info on here about swimming, just search around and you'll be loaded down with reading.

The pool water will feel just fine to you once you get moving. If you are only swimming a short distance then you are never gettting warmed up and therefore the water continues to feel cold. Read a bunch of the other threads and then ask some questions based on what you have read and where you are in your training. You have a lot of time to get ready and if you learn a couple of basic techniques you'll be swimming a mile+ in no-time.

Wet suits are a great help in cooler water. I swam in 52° water this March with a sleeveless suit and it wasn't tooooo bad. The suit also provides some much needed bouyancy that could be very important to a less confident swimmer. And yes you can roll over and bacstroke. Lots of peole do it and there is no shame in it.

You might want to look for some indoor tri's first. They are pool swims and that could help boost your confidence in the water. See if your gym has a masters class. Many are offered for a small fee (mine is free with gym membership). Talk to the coaches and other swimmers. Get a few tips and some drills to work on. Don't try to do everything at once. Work on one drill at a time and master it then move on. Trying to think about arm position, body rotation, looking down, breathing styles, what to do with your feet, etc. can be overwhelming so take it slow - you have time.

Good luck and check back with updates. Everyone here is more than willing to help.

Welcome to the wonderful world of Triathlon.