Coughing, sneezing and spitting through a regulator are no problem. You can even puke through one if the urge hits you and then you'll get some close-up views of the reef fishes. Your loss is their gain!
If you had a friend who had never skied before, but thought they might be interested in trying it, would you suggest they read a book, watch a video, or go to ski school? I'm betting you picked ski school because it's really the only way for your friend to find out for sure. Be as kind to yourself as you would your friend and go to SCUBA school. Even if you don't like it, which is highly unlikely, you'll get that spongey head of yours filled with some neat info. on physics, human anatomy, the atmosphere, tides and currents, the underwater environment and all sorts of other cool stuff that you might find useful in other areas of your life.
Ask around though, and find a good instructor. Ask the instructor for referrences from people he/she has certified recently or up to a couple of years ago. Then contact those folks and ask them how their experience was with the instructor and how they've gotten along on their own in the sport with what they learned from their instructor. Ask if anyone else in their cert. class had problems and if they'd recommend that instructor to others. Once you pick an instructor, let him/her know you're a little apprehensive about the sport and if he/she doesn't respond to that in a manner you're comfortable with, continue your search for an instructor you want to work with and one that wants to work with you. It's a great sport, if you're into skiing, I can't imagine you not really liking SCUBA also. Just don't try to do both in the same day, to find out why, take the class.
I'd also highly recommend reading Walters post here 
