With those engines it's the cooliung system that got the bad reputation. Later blocks are far better but they say that if it's overheated a couple of time it's likely to suffer from cracking the block where the cylinder meets the top deck.
Look at the state of the oil and the insides of the engine through the filler, at 50,000 miles it should still be clean and light brown, not stained black from old oil.
Check the state of the cooling system, the viscous fan etc, has it been run with a good cooling system or a bad one which could indicate the engine has been put at risk.
The 4.6 should run smoothly with a standard exhaust, so if it burbles it might need a valve.
Look for the usual leaks of coolant and oil, are they long-established or new.
If the engine is ok then go on to check the auto box, you should look at the workshop manual for the road test procedure.
Air suspension, does it do what it should?
