Installing an IGH in a Trek District SSB I own a Trek District SSB, which uses Trek's proprietary belt drive system. I'd wanted a bike with an internal gear hub, but they only offered a 3-speed version as an upgrade, so I decided to buy the SSB and upgrade it myself to something a little beefier.

The SSB has the same frame as the IGH 3, so it already has the cable guides for the hub. I'm going to take my bike to a local community shop to do the conversion, so I should have people on hand to help me with any problems I run into. What I am looking for help with is my shopping list (although warnings and gotchas are welcome).

The IGH 3 claims to use a Shimano Nexus 3-speed hub in the specs, but shows a picture of a Shimano Alfine hub. Would this work, plus this shifter? Will I be able to swap the drivetrain components over from the SSB to the new hub, or do I need to order replacements for anything?

(Referring to this question, it sounds like an Alfine hub should be compatible. I'm still uncertain about exactly which other components I'll need to order.)
Checked with Trek, and that is a 135mm spaced frame, so yes, that hub should work fine with it.  I would make sure of the interface for the belt drive "cog" on the rear wheel, make sure it will work with that hub.  Otherwise, that Alfine should be very good.  That shifter should work fine with that hub too.  Making that interface question the only issue I see other than building the wheel if that's your plan.  If you've never done it before, be aware it's a lot more involved than it appears.