I'd probably tell them how to do it and provide some direction while they saved themselves some money.
With the light weight of the Zuk transmission, there's really no reason not to do it yourself. You don't need any special tools outside of a 12, 14, and 17mm wrench.
To answer you though, I'd probably plan on about an hour from start to finish and would go off that estimate.
For the cost of a shop doing it though, you might really want to consider buying a factory manual, your own TO bearing, doing it yourself, and go out for some pizza and beer for the next couple night with all your leftover cash you didn't have to spend.