Key thing with the early V8 is being absolutely 1,000% certain the timing belt, tensioners, water pump and thermostat have been changed on time at 5 years or 80,000 miles, whichever comes first.
If the belt lets go, the engine is toast so if you don't know, it needs doing ASAP.
Also, unless there is history it has been done, you need to change the ATF in the gearbox, the front and rear diff oil, and the transfer box oil which you buy in the right 850ml bottle from the VW dealer. VW will tell you these are sealed for life units. That's bollocks.
Brake fluid should be changed every two years too.
Read the buying a used Touareg thread - link in my signature below. You'll learn a lot and will know what goes wrong.