Considering 2500 Purchase...Help!

Here's the deal:

'00 ('01-'02 style front)Chevy Silverado 2500 4x4 LT Extended Cab Short Bed (6.0 engine) w/47000 miles. Looks and drives clean. $19,500.00

My questions:
Does the price sound right?

If you own this model are you happy with it?

I've heard of the following potential issues so far: Valve knock, Cylinder "slap", electrical problems. How common are these issues?

Are there other potential issues I should know about?

I have a '01 2500 4x4 LS ext cab short bed 6.0 with 42000 miles and i love it. I got it for my 18th B-day so Ive had it since September and no problems. Since I got it i added flowmaster 50 series dual exhaust and a k&n air filter. I only complain about the gas mileage 11-14 but..... i also have a heavy foot due to liking to hear the exhaust. but i would like to think you could get around 13-16 with a lighter foot. The price sounds about right mine was around 19500 give or take a little with 39500 miles on it. I havent noticed any valve knockin or piston slap but... i dont think i would know what that sounded like in the first place. im new to the world of adding modds and fixing engin problemsso sorry no help there, but I really love mine so I hope this helps you make a good decision.