Engine Mechanical problem
2000 Toyota Tundra V8 Two Wheel Drive Automatic 98000 miles

I tow a camper wth my Tundra, approx. 5000 lbs. The Tundra has a tow rating of 7200 lbs.
My question is, " is there some point that, due to the mileage & age, that I should be concerned about towing with my vechicle?', ie, does towing a trailer, over time, put excessive stress on the engine to the point that you should not tow with it?
I should also state that at 90,000 miles I had to have the heads resurfaced at a cost of $2500, which to this day I do not understand, because the truck never has overheated.

Thanks