I replaced the Transmission range sensor ( on the side of the gearbox ) on a A4B5 v6 2.4 & while it wasn't easy. There's not much space & you want a low profile thru hole rachet with a torx bit, it's not near impossible if you have good access under the car.
I took the old range sensor apart & it had broken up inside into a bunch a pieces.

unfortunately replacing it exposed a different problem & by using a cheap rosstec OBD2 I find that it's not detecting 3 solenoids in the gearbox, so I expect theres either connection problems in the loom to the gearbox. Or the silly plastic printed circuit strip connector inside the gearbox that pushes onto the solenoid connections. I think I have this problem in two b5 v6 cars.
And I need to replace the transmission range sensor in a B6 3.0 too. ( Different plugs on the end, the By has a flat plug. The b5 has a round plug.