Most churches will do marriage counseling for church members. My dad did those for a long long time, with some really great success stories. There was one where the guy insisted on honeymooning by backpacking in Death Valley, and we're still not sure that marriage is a winner, but most of the others came out pretty well.
Many churches won't do the marriage unless some requesite counseling has been done!
That said, I'll second the opinions of most of the others here -- if you get a good counselor, and if you and your partner approach it with the attitude of "preventative maintenance," rather than "provocative maintenance" it can be very beneficial. If you come at it with wrong attitudes, it'll be a waste of time and money. Oh, no it won't -- you're not married yet. If you come into it wrong and discover that she's not the one, you haven't signed the marriage stuff yet, so you're golden: marriage counseling could save you from making a poor choice.
Best wishes to ya,
Dan