I've done a few of these, and have some advice for you:
- Glad you like your new training plan. The amount of hours in the original plan for a 1/2 sounded high, although admittedly I've been lazy training for my last two
- Keep up the swimming, especially if you aren't used to it. But once you can swim the distance (1.2 mi), concentrate on getting faster with intervals
- If it's an open water swim, go do some open water swims. It's a different feeling to be in the middle of a lake etc. swimming far from the shore
- Find out what they're serving at the race (e.g. Powerade, Gatorade, etc), and do some training with those brands / flavors. You don't want your stomach (and you) to be unpleasantly surprised during the race
- Stick to your plan during the race, keep your HR in the right zone.
Good luck!