Do you bother with Rust Check or undercoating?
I have never heard of "Rust Check", but I will look into. So I can the answer to part "A" is "No, I did not use rust check."
As for part "B", under coating. I do not think that would have helped me here. The frame was fine. It was the hardware on the brakes and the exhaust system as well as the windsheild frame.
I think had I washed the vehicle more frequently I would have less rust.
At the end of the day, I think I was happy to have this situation. I am enjoying my new ride.
Top Benefits
1. If I need to go under the hood (and I don't), I can use the hood release lever instead of a pair of pliers. And, I can actually shut the hood without a screw driver in hand.
2. If I want to change the temperature from Hot to Cold to Hot, I can use the dial in the truck rather getting out to the passenger side, reaching under the dash and moving the lever by hand.
3. I can actually use the key to unlock the doors. In my old truck I never did this until my battery discharged and I tried to open with the key. All of the locks were frozen (had to jimmy my way into the car).
I guess I sort of "saved up my repairs" to justify buying a new 4Runner. However, at the end of the day... 10+ Years and 247K Miles... it didn't owe me a thing.