Not sure about the driveshafts. I assume they're the same for all FWD. I think it's just the 4WD with transfer box that has a shorter offside shaft?
Not sure about the cost but I'm guessing around the £2000+ mark for a professional job, inc s/h parts.
DSG boxes go for about £500-£800 depending on mileage. Probably another £500 for the steering wheel, pedals and bits n bobs.
That's about the same cost as a Helix clutch fitted by a garage, so I think the extra ££s is worth it to ditch the manual
Manuals with uprated clutches are just a pain in the arse in heavy traffic, which is pretty much a daily occurrence for me. I've got RCLS big time (Ripped Clutch Leg Syndrome) and getting tired of it tbh.