It'll be a lot easier if you detach the shift cable. Shift the hub down into first gear (with the least amount of tension in the cable) and find the spring loaded arm where the cable attaches to the hub. Push the arm up and you should be able to pop the cable and attached nut out of its place in the arm, then remove the hub with a 15mm wrench. I'm sure someone will be able to post a lesson with pictures (possibly including the real names for all the parts).

As a heads up, the fender clearence on the Seek is very tight. For this reason, you'll find a threaded boss about a third of the way up the seat tube from the bottom bracket (it looks like a water bottle bolt on the wrong side). Use this rather than the chainstay bridge to install your rear fender and you'll have better clearence with wide tires and a few inches more coverage on the back.