This is where it's really helpful if you have pressed each block very carefully as you made it, and pressed each seam joining blocks also. Then there should be no additional pressing to do.
As for the back, I discovered recently that you can mist the back after it has been loaded on the longarm and the wrinkles just fall out. If you're sending the back out to a longarmer, you might ask her if she needs you to press it or if she is okay with using the mist-it method. Some longarmers are nervous about applying any water to a customer's quilt, but if you give permission she might be able to do it for you. There shouldn't be a charge as it takes no time at all to do.