I'd like to add my 2¢ to this thread, however old. I'm in the process of replacing both the top and bottom gaskets on my 2004; still waiting on the bottom one. Like HooDoo says, originally there is a gray/black soft sealant of some kind. It is slightly sticky but can be wiped off with a rag. Inside the crevices of the gasket's edges there seems to be more of it, but it's at the very inside edge, so not touching the metal.
You don't want to put a permanent sealer inside there because if you have to replace that gasket again you'll have a difficult time getting the old one out. It has to be a soft compound of some type (and very little) or else just put it in there dry. That's what the dealership I bought mine from said to do, just put it in there dry.
On mine, the inner portion of the outside edge has a very small amount of rust, mostly like a stain. I'm going to try to get some of the goo out of the old gasket and put it on the outside edge where the rust is forming.
Rich