I have had very good luck with wetting and blocking. I have done it with individual blocks on numerous occassions with outstanding results. I would say try doing it with your quilt top. Just make sure you let it dry all the way before removing the pins. It should keep the blocked shape and not revert back if it isn't too bad.
I am sure you will have good results. Once you do this I would recommend pressing and starching it well so it will not distort in the quilting process. Actually I have read here where some use starch in the blocking process so you could try that as well.