In looking under the hood I cannot tell if the wiring from the fuse panel to the engine compartment through the firewall is continuous, or if there is a giant connector at the firewall. It appears to be a giant connector unit. Is this the case? If so, has anyone ever seen electrical problems result from bad connections here, even though the connector has not been disturbed in any way?

 

It's a bulkhead connector, it's just a big plug held there (to the other half inside the car) by a 10mm (or so) bolt.

If its's never been disturbed, there's no real reason to suspect a problem there, not to say it's impossible tho.