I have some more information and pictures about this operation. I was confused because I didn't see any o-rings when I removed the bleeder cap.
The cap
Some of the posts made me think that maybe some tanks didn't have o-rings but I finally managed to wiggle the part with the 8 bolt holes and realized it was a separate piece. It's hard to pull out but I got some big channel locks on it a eventually wiggled it enough to get it out.
Below are pictures of the tank with and without the o-rings.
O-rings don't seal by vertical compression like a gasket. They are squeezed between the OD of the male part and the ID of the female part. I could feel the old o-rings had become kind of square shaped and might not seal anymore. I have a feeling that some of the threads about condensation on the trunk lid near the coolant fill are due to these o-ring seals.
I visited the hardware store and got some generic o-rings since the Porsche parts place didn't include the genuine ones in my order even though I specifically added them to my online cart. They did give me a credit for the unshipped items.
I haven't driven the car yet but the housing felt good going together over the hardware store o-rings some I'm hopefull.