Spoke to Gary at Renntech. Back to the dueling mechanics. You know doing expert arguments by proxy is not nearly as fun as it sounds. I got two mechanics that both have 15+ years of Porsche experience each and when they disagree, what the hell can I really do?
Gary says the seal can be installed from the outside (which Steve at Dieter's said is not possible). Regardless, Gary will install it before sending the transmission back, so frankly, i couldn't really care less how it get's in there. He also said, the clutch disc could be re-used, a claim that both Steve at Dieter's and the rep from Pelican dispute, but he also said he'll replace it. I hope he actually replaces it with a Sachs Power Clutch disc.
The story as to why the seal wasn't in there in the first place is a bit hinky, if you ask me, but i'll let that go.
As of right now, it looks like he is going to do right by me and I'll have the transmission back next week. Here's hoping.