Like you I'm hooked on tri's and the board! so i'm going to put my 2cents in: OH, YES IT CAN BE DONE!!!! AND MORE QUICKLY THAN YOU THINK!!!!
As a competitive swimmer from age 4 and a USS swimmer from age 8, also after experiencing a very good friend of mine who can swim a basic stroke who wanted to do tri's: this is my advice (AFTER YOU HAVE ACCOMPLISHED THE PREVIOUS POSTINGS ADVICE and have become comfortable swimming a 1/2 mile without major struggles):
I advise you to work on "looking at where you are going": stick your head directly up out of the water ahead of you while you are swimming to see where you are going. It doesn't have to be very high, just enough to see ahead of you, not even high enough to take a breathe even (not that you couldn't do that). (This would be like one would do taking a breathe during breaststroke, only your doing the front crawl). Because if you can't see where you are going you will not swim straight. And zig-zagging, or worse swimming in circles (one arm is usually pulls stronger), will take much much longer and ware you down. Even popping your head up and looking where you are going you will still zig-zag a little bit but not nearly as much. I don't know any swimmer, even olympians who can swim completely straight in open water a long distance. So don't fret too much.
So, start out with at least one pop-up per length of the pool, or one every few lengths until you get to one a length. Once you get used to it you will figure out how much you will need to do it when in open water. It's kind of an as-needed thing, looking every few strokes will make your neck sore and slow you down too. so just as often as you feel comfortable when you do open swim (you will have to dodge other swimmers, etc.). Oh and if you are as unlucky as I was in my first race, on the way back swimming we were directly swimming into the morning sun. I couldn't see anything at all. So I had to look to the sides and I still got off course, thinking the furthest buoy marker was the one I needed to be near, only to find out (thankfully quickly) that it was the wrong buoy! But alas I still made it out 2nd or 3rd out of the water in my age group. So no worries!
So: after you get comfortable in the swimming then try to do the head pops, I wouldn't advise both at the same time, you need to learn proper stroke first. Worse case you can stop and tread water to see where you are going for your first tri. I even had to stop a few times swimming into the sun like I did. It's no big deal TONS of people do it. But the head pop thing is more effecient when you are at that stage.
Also I would do an open water swim at least once before you race, even if it's within a week of your event. Even if it's only a few yards. You just need to get used to the water buoyancy and the feeling of not being able to touch bottom and rest! I think you can rest on a boat for a second or two if needed; if nothing else you can stop and tread water for as long as needed to rest. Wetsuits do help with buoyancy. Make sure the water isn't too cold though. There will be volunteers in many boats along the course for any reason at all.
Actually I feel just as nervous about my run as you are in your swim. I have yet to run a straight 5 miles without walking even about 10 steps at least once mainly because I doubt myself having never been a runner, EVER! I had a skiing accident years ago when I was 13 and thought I would destroy my knees if I ever ran long distances (never did any running besides soccer before). I am now 35 and have to retrain myself to think differently as all is ok! Yes I realize that I could walk a whole race, and swimming is much more complicated, but the point is the same: some day you will soon swim like a shark, and some day I will soon run like a cheetah!!!!!!!
Tri's can definitely be complicated at first glance! But boy they are fun as **** !!!!!
Good luck and I hope that I was of some help! YOU CAN LEARN TO SWIM EFFICIENTLY IN TIME!!!!!! You will be so hooked after your first tri!