You should flush radiator as part of the repair. Here is the flow chart of how water moves in the system. Hot water from engine is "sampled" by those four holes on that bypass disk. That allows hot engine water to mix with cool radiator water and warm up the stat so it will open.

 

Thank you so much, guys!!! I really appreciate the help, and I'm glad that it wasn't anything too major. I'll keep you all posted.

 

Let us hope so. But frequently the outcome of a gross overheat is damage to head gaskets, warped head, slipped sleeve, and/or warped block. What you are dealing with has the potential to be something major, and you won't know until you make proper repairs. Would suggest that in addition to daily fluid level checks for first eweek, dropping back to normal weekly checks after that; you should celebrate your good fortune (if indeed no more damage) by adding an Ultra Gauge. It is a code scanner/display/alarm monitor that watches data from the OBDII port, so you can see temps in digital fashion and real time. With one, you would have seen engine temp rising before gauge started to go up. About $70. While you have system repair underway would suggest good flush of radiator, crud in radiator reduces cooling, and flakes of it can clog the new thermostat little holes, making truck run hotter.

 

T-stat, replace it along the hoses, clamps, flush the system. if this is not something you want to do as ljdiscovery suggests, sell the truck right now.
It is the most basic of repairs that you will ever do, compare to some of the ones await you.
With that kind of milage if you dont have reciepts the size of a telephone book, you are going to be replacing and repairing a lot of stuff in your future.

 

Replace all the squeeze together spring type factory hose clamps with good quality (which usually means American made) screw type hose clamps.