Ok, here's the latest.
I went down to the truck this morning, and tried the old starter relay. I could feel the starer relay "switch" in my hand when trying to start the truck, but -no response from the starter-. I then bypassed the relay entirely (thanks mangus!!) at the relay-plug and the starter began to whirr, but would not crank the engine.
So, it appears the original problem WAS the starter relay, and I probably burnt out the starter itself with my unintentional welding project when i crossed the posts on the starter with a bolt.
So, now I just need a proper relay, and a new starter, but I had to have the truck towed this morning since the lot owner was giving ultimatums to have it towed within the hour.
Thanks to everyone for their help on this, I sincerely appreciate it. I have learned an awful lot about the starting system in this truck, which I'm sure will prove to be quite valuable in the future.
Thanks.