Months and months ago, I messed up my Nexus 8 speed hub...bungie cord-steel "S" hook and a popped rear gear. it's been a problem ever since, a drag/braking feeling... Finally ordered a new wheel with an Alfine (higher level Shimano 8 gear hub), laced into a Sun Rim.
I thought the wheel would come with a 20 tooth sprocket and new non-rotating washers. (it did not)
I thought it would be a breeze to change wheels. (it was not)
Like an old boss of mine would say: "there you go think'n again..."
OK, so the wheel arrived nicely packaged, perfectly true and plastic wrapped with two dust protecting rings in a bag, a set of multi-language instructions and a receipt.
If you've never taken off an internal gear hub wheel before, I suggest you read instructions. There is a series of rings and dot-positions you need to know about and how they work together to get the wheel off the bike.
I had to remove my 18 tooth gear from the old wheel. Not an easy task if you've never done it before. There is a lock ring, tight against the gear. A flat head screwdriver is needed to pry the lock ring off, getting it back on the new wheel is difficult, but can be done with patience and sore fingers.
I used brand new cloth velo tape for the rim, dusted my Presta valved tube and put on the 700x38 Nimbus tire. did the usual alignment stuff... adjust... adjust ... brakes... adjust.
When it was all done, the new Alfine hub is a gem. It rolls so nicely, shifts gears without hesitation, looks fantastic and the wheel feels good so far. I wish my bike had come with Alfine to start with.
Just a warning to folks on the forum... Internal Gear Hubs, Nexus & Alfine are more complicated that you might imagine. (At least for people like me who are not bike mechanics) If you have doubts about your ability to deal with gear swapping, you might do best to find a good bike mechanic.