So I did this in another car (I'm sure it's about the same) that it took two days. Once they got the foam in, I dropped the care off and it was just a matter of the guy taking the seat out, taking off the cover. Reshaping the new foam and applying the adhesive and reapplying the leather.
I was charged 70 dollars but I'm assuming most of that was just for taking the seat out of the car.
I don't think anyone can answer how long foam will talk to get in. You would need to discuss that with the guy that's doing your seat. But that doesn't matter as you can still drive you car until he gets what you need in.
I took the seat out of the Passat when I was doing an Alarm upgrade and it's really not that difficult. If you were confident in your abilities you could probably change the seat foam yourself.
I was given this rating for foam:
Here is the grid rating
CF-NT Extra Soft Seats for infants, cover for stiffer material, bedding applications
CF-40 Very Soft Seats for children, cover for stiffer material
CF-42 Soft Seats for 115 lb. person 3"-4" seat pad
CF-45 Firm Seats for 170 lb. person 3"-4" seat pad
CF-47 Very Firm Seats for 200+ lb. person, or seat in hot-humid environment for 170 lb. person.