Zarbuck,
You need to do more reading and understand the 944 better.
Clark's Garage Home Page
Buying a 944 that has electical problems and paying a mechanic it do the work is not a good idea. You have to do the work to understand why the part failed. If not, you car will be in the shop or parked and you will spend a lot of money foolishly.
The "brain" or Motronic DME is the computer that has to be treated carefully or it will burn out and you will spend another $350 to $500 for a new one and pay a mechanic to have it insatlled.
Dead batteries, bad alternators, battery cables with corrosion and bad ground will kill a DME.
Never jump a 944 or use a battery boost pack to start!
Take car of the DME:
Is the new alternator charging the battery?
What is the battery voltage?
Did you clean all the engine and cabin grounds?
Do you have a volt-amp-ohm meter?
Read Clarks for the info?
GL & welcome
John