Phaeton first purchase

Good day to each other, at the risk that you will have to read the questions for the 40th time, I would still like to ask a few things I will sell my previous pass in October. Now I have been looking for a bigger, even more massive car for a few weeks/months and have come across the Phaeton. Financially, the car is very tempting compared to A6 etc. without any equipment for almost the same money. Do you have to pay attention to something special regarding year of construction/running performance? Can you take good care of a 2006er with 125,000km (3.0l TDI 4motion)? How are the spare parts prices in general compared to the passat? And: Can you compare repairs/service with an Audi A8/Mercedes S 320? My father-in-law owns a workshop and just above all cars. Would you like to know whether I can make small things/carryings there or have to be a ceremonial. Phaeton service partner.