68 Baracuda electrical questions

The BEST wiring diagrams are those in the shop manual.
Trace or copy the circuit you are interested in to create a clearer working diagram and schematic.
The circuit will make much more sense when you have done this yourself.

One of our members here has redrawn those diagrams in color with layers to help make this easier.
https://www.forabodiesonly.com/mopar/attachments/68-barracuda-factory-wiring-rev-2-pdf.1715189875/
Removing, and cleaning isn't that hard
https://www.forabodiesonly.com/mopa...ain-bulkhead-connector.452501/post-1972795847
https://www.forabodiesonly.com/mopar/threads/cleaning-bulkhead-connectors.446706/It will not hurt to get new seals as well.

Removing the connector engine side. question on the main harness plug on firewall

Repairing and replacing terminals or wire sections requires some tools and a little practice.
The correct terminals are needed to insure a) they aren't loose in the connector housing b) the wire crimp has minmal resistance.
https://www.forabodiesonly.com/mopar/threads/sources-for-chrysler-type-wire-terminals.418908/