Need advice before I pick up my TT It's a 750 tow

I'd be a little concerned at taking a truck with almost 300,000 miles on it and expecting it to work at its maximum rated capacity, no matter how reliable it's been or how well it has been maintained.

That said, assuming all goes well you probably won't think it's too bad on the trip home with the EMPTY trailer. After you add 1500lbs of water, food, tools, toys, equipment, etc., you might not like it as well.