[AndrewJ]

About the chain:
If you're seeing that the leading edges of your cassette are rounded off then you're chain has already stretched. Damage done.
You can try to put a new chain on and see what happens, but if the old chain's been there long enough a new chain will just skip under pressure. So be careful when coming out of the saddle for the first time with a new chain.

If the new chain skips, then it's time for a new cassette, your chainring you can probably just flip around (as long as it's not ramped/pinned for shifting)


On the Hubs:
You can (probably) just take the wheels off, remove the axles and fish all the little ball bearings out of there. Just make sure you don't lose any.
Clean them up with some WD-40 and inspect them for any pitting. Same goes for the bearing races inside the hub.

Once they're clean and passed inspection put them back in with a fresh helping of grease.

That should hold you over for another year.


If you use your bike every day (for commuting and such) then it's a good idea to repack your hubs and replace your chain about twice per year.

If you use the bike less, then once a year should do it.


Oh, and loose-bearing hubs are functionally the same as sealed-bearing hubs. They can get more dirt and junk in them, but they are easier to clean out and repack. With sealed bearing hubs you'll have to pull the entire bearing and replace it if it's bad.

I guess what it all boils down to is that sealed bearing hubs are a little more $$ and a little less maintenance. Loose-bearing hubs are the other way around. Take yer pick.