if you have a donor CR170 DSG scrapper you could get all the parts and wiring looms from in one go then it would be possible, though I'm honestly not sure if it would be worth it vs. the cost of selling up and buying a DSG model instead.
If you didn't have access to a donor car then, IMO, it's not worth attempting.
Off the top of my head you'd need the following (may not be a complete list...)
Gearbox, including mechatronics (gearbox code LTD is the correct one for the Leon CR170)
Gearbox to chassis mounts
Flywheel
Driveshafts
Cooling system plumbing for DSG oil cooler
Engine bay wiring loom
DSG shifter assembly and selector cable
Wiring loom for shifter
DSG gearknob and gaiter
Steering wheel paddles
ABS unit that can be activated for hill hold (if the current one doesn't provide this)
Foot pedal assembly for automatic models
VCDS or similar would be required for coding and adaption too.