(((HUGS))) you know, it can be very hard and scary and painful, but it also can be wonderful and enlightening and liberating. 3 visits most likely won't scratch the surface, but if you can swing more, and get the right therapist, it can be the best gift you ever give yourself and your husband.
I wish you well. my dh and I have gone thru marriage counseling and there have been really tough sessions, and really wonderful sessions, and I have to say even the tough ones have been some of the best ones.
I absolutely agree about looking into individual sessions, too, especially if they are covered, to help enhance/help you each process the mc sessions. and do your work! ask for books/homework, etc, from your MC, to help enhance the sessions, then do it. there are a lot of people who go into mc who don't go into it looking to really do the work and it ends up not being nearly as effective as it can be.
good luck!