I've done some more research on this with the goal of understanding the mirror wiring. Here's the connector that attaches the wiring harness to my current non-memory mirrors:
Note that there are quite a few empty sockets in the connector.
Here's a picture of one of the wires from the harness that I have:
Note that at the end of the wires there are two male terminals that appear like they will fit inside the connector of the mirror control.
I think that the way this works is that there are two possible sources for the control signal of each mirror. One is from the switch near the driver's-side window and the other is from the memory control under the seat. So, when you control the mirror manually the signal comes from the control on the drivers door. When the memory unit takes over, it comes from the control box under the seat.
Unfortunately, I do not have one complete intact harness. So, I'm going to have to scrounge for some parts before I can check my assumptions.
Also, I found out that Porsche changed the configuration of the memory control in the 2001 model year. According to my Bentley Manual (page 02-25) when Porsche added the electronic front and rear lid releases they also added the individual key programming feature. So, I don't think that feature is available in my 2000. It may be better for me to use the wiring diagram from the 1998 vehicle than for the 2002 vehicle.