I'm looking at getting an A4 tdi as my next car but I'm unsure what spec came with what trim etc?

What at sort of mileage do things start to go wrong at? Lots I've seen have 130k+, I've had diesel mondeo's in the past at this mileage that sound like a bag of nails, is that the case with these engines?

How reliable are the quattro's? Do they sap any economy?

Im only wanting to spend between 2-3k and ideally want an 03-53 plate 6 speed 130bhp model in estate form with reasonable mileage but I know I'm wanting too much for my budget and most likely will end up with a saloon.

Any advice would be welcomed,

Pete