healthservices,
Replacing the Immobilizer from your Boxster will require programming.
Since you mentioned about putting a matching DME Set from another car let me advise you against that.
From reading your notes it sounds like you want to put as little money into the car as possible.
We made about video about why this is a bad idea:
https://youtu.be/QCOunBZL_Yk
VIN # will be different in DME and therefore that can open a can of worms.
It's much cleaner and simpler to solve the issue with the OEM set that you currently have.