I was able to rebuild the transmission jack, but I could not find a replacement seal like the original. So I had to adapt a standard u-cup seal to make the repair. This seems to be par for the course for inexpensive Chinese made hydraulic equipment. My hack is explained here:
https://www.garagejournal.com/forum/threads/fixing-my-transmission-jack-and-engine-hoist-hydraulic-cylinder-seals.530957/
I added oil pressure gauges to both my Boxsters, in the original green 2000 base I installed a 996 sender with output for a gauge plus the output for the warning light along with a VDO gauge. When replacing the blown engine in my 2000 S I used a cheap gauge and sender bought off Amazon (which works fine except that the sender failed after a while, I installed a new sender and it is OK). Since I am selling the base I decided to swap the (expensive) VDO gauge and 996 sender to my S. Today I swapped over the gauge but it will be awhile before I switch the sensors... and lo and behold... the VDO gauge gives me about half the oil pressure on startup. So it seems that you cannot use a cheap Amazon sender with a VDO (Porsche) gauge... or vice versa.
The engine that is going back in the car is now under the car, I was waiting for my transmission jack to start the installation... so I hope to start that process tomorrow.