There are lots of guys who went through with contacts. The instructors don't mandate whether you do or don't wear contacts in the pool but it doesn't really work well if you don't use daily contacts anyway. I would recommend practicing swimming without contacts if possible.

I would practice by just floating in the water with a mask on and pretending to pass the snorkel to your buddy by taking it out of your mouth and putting it back in. Then practice by doing it with your mask off as well.