This is for your "new" CrossCheck? Check the Surly website (www.surlybikes.com), the CrossCheck will take either 130mm or 135mm hubs.

That dimension is the distance between the dropouts -- measure precisely where the rear hub fits. Many frame makers, Surly included, make their frames with 132.5mm dropouts, so that the frame will take either 130mm hubs (road standard), or 135mm hubs (mtn bike standard). Of course, the frame has to flex 2.5mm with either hub, but with a steel frame, it's no problem. Unless you have a good reason (say you have a bunch of road hubs laying around), I'd go with the 135mm hubs for a CrossCheck, they're theoretically a bit stronger.

The "WE" numbers appear to be Harris Cyclery's own part numbers. The difference between all three wheels (as far as I can tell from the website) is the hubs. Basically, you get what you pay for, but I don't see how you could go wrong with the Nexave hubs. Harris says they're "Deore LX" quality, which is perfectly adequate for all kinds of riding, even cross-country touring. I'd consider higher quality hubs if I was: 1) Carrying a huge load, 2) Facing weeks of monsoon or muddy conditions, or 3) Heading to remote corners, like the Silk Road.

I can't comment specifically on the rims or Harris' build (I build my own wheels), but Mavics are frequently recommended. I'd trust Harris, and I'd trust their comment: "These wheelsets are excellent for touring bikes."

To change the cassette, you need a cassette lockring tool (example), and a chain whip (example). There are more portable solutions, but for working at home, these are good choices.

-- Mark