Thanks a bunch for the insight folks, I really appreciate it. Although I only drove it while overheating for a moment or two while looking for a safe place to pull over, it certainly seemed like an eternity to me. I'm really hoping the HG isn't toast, but I guess I'll cross that bridge when I get to it. I did pull the dipstick yesterday and the oil is still oil colored, no creaminess or milkiness but I guess it's a little early to tell.

I'll be sure to use the appropriate coolant as suggested, and will do my best to purge the system as recommended. Hopefully I don't run into any problems swapping one rad for the other.

... about that oil. I never would have thought to use diesel oil in a gas engine. Pardon my ignorance, but what's the deal with that?