Bratface:Practice breathing in the car at stop lights. It will become more natural the more you do it. Good luck in your class.
I tried that once... The mask wasn't too bad, but I needed to stick the snorkel out through the sunroof...
Retired - Breathing getting easier, and air comsumption going down with practice is one of the most common bits of advice on this board. Just stay with it - it will get better - I certified at 50. Good Luck, and let us know how you're doing!