I will tell you that a 51k mile Tahoe from 2002 is not worth more than a 150k rig in my book. Vehicles that sit or are driven short distances are plagued with different issues. My 325k mile tahoe is in much better shape than than yours, cleaner engine bay and upgraded components. Rubber and gaskets dry out and deteriorate over time. I'm willing to bet this thing leaks just like any other high mileage rig. I'd recommend some common sense and not ask for feedback on a vehicle with a torn up front end, signs of rust and plenty of other visible cosmetic issues. Personally I would skip passed your truck if I saw it in an add and was shopping for a vehicle.
Parts truck good for an LS swap maybe $1500-$2000 around here.