Update: Thank you all for your help -- success! Took a while but couldn't have done it without your suggestions. I'll summarize to perhaps help another.
Bought a flat punch and a breaker bar, as well as a pipe to further extend leverage but the pipe didn't turn out to be necessary. I actually bought an assortment of punch tools in case I would need to put in an indent as suggested, but extras weren't needed either (at least this time).
Had room to tap the punch in the center (after applying more PB penetrating oil), then used breaker bar with my hex socket & after a mighty pull, was able to remove with just a few skinned knuckles. It was a pretty sudden & violent release, but no real harm.
After that, was able to change oil without incident, but lots of hours in total to get to that point.
Project, yes it is true that Porsche doesn't suggest changing at the interval of 30K, but Wayne's book suggests every 30k/2yrs is preferred in his view, & since I was at year 11, it was time for the change me thinks. There oil was fairly dirty, with some small bits of metal, so I'm glad I changed it.
TRK, I'm sure you are strong like bull, but i'm telling you this was a :troll:. Yes, I knew the 6 speed is different than the 5 speed, but Wayne's 6 speed photo turns out to be from a 996 & that 6 speed case turns out to be a different animal than the Boxster 6 speed case - which I didn't suspect...
Thanks again everyone!