Congratulations Tango for your Q4 and welcome!
Concerning the timing belt on that engine i can give you a few advices:
Official maintenance information says: "changing the timing gear drive belt every 120.000 km" only. Well, that seems much in comparison to what the other guys said. I guess it also depends on the way the car has been driven!
On the other hand, on my Q4 i had the timing belt broken at about 90.000 km!!! It was a lot of work taking down the cylinder head and changing all 16 valves. BUT: It was not the belt that was too old or so, it was a small screw that fixes a sheet metal cover inside the path of the timing belt that untightened itself by motor vibrations, fallen into the belt's drive path and teared the timing and balance shaft belts into pieces. So be very, very careful when you remount your new belts and covers. Fix all the screws around there very well with Loctite!!!
To change the belts you will have to lift your car at the right front wheel, take the wheel and the covers inside the wheel housing off and eventually take down one bar that holds the engine to the chassis (the one upside next to the water reservoirs). Everything should be logic after that. You don't need any special tools. There's not much space round there, but it's possible to do.
Have fun with your car!!