DemonSVT has a nice write up of how to gut the manifolds on his website. Use that but skip all the parts after you get them unbolted. Then replace the gasket as Lance said, and put them back on. The write up will basically tell you how to access the bolts you need, front or back.
Just search around for his name, and I believe the link to his website is in his sig. I would post it, but its not mine so I wont. You should be able to find him easily in the 3L or F.I. forums.
