Etienne:
Julian has answered most of your questions. I don't have experience of the Alfine 11-speed but of the Nexus 8-speed on which it is based. The gear gable has two attachments that are a fixed distance apart, one on the gearbox, one on the frame. The one on the gearbox is a nut on a bolt with a hole through it fixed on the cable, and is released by pulling down a springloaded part of the gearbox mechanism and pulling the nut free from a metal hook. The frameside fitting is a slit runner, so you pull back the bullet cap on the case until the inner cable can come free through the slot. Practice at home and it takes seconds to release and fit. Don't practice at home and you might find the fitting part, in which you have to twist the cable just so to line up the nut with the hook, a bit frustrating.
André Jute
