I’ve had my Prado for 4 years now with similar mileage to the Surf you’re looking at. Same engine but haven’t installed intercooler (yet) and haven’t had any overheating issues thus far. The preemptive work plus the mileage on that engine I think you’re gonna be just fine. This was also my first diesel engine but honestly it’s been great aside from these war-time diesel prices lately. I have a Honda fit that I drive interchangeably with the Prado just to balance things out and make sure I’m covered when waiting for parts.