I decided to buy a new rear hub that'll take 9/10 speed, a 2013 LX to replace the existing 1990 LX. I'll take the advice above now that I have the tool.

I went with a new LX rather than XT because I've been reading about the smaller bearings on the XT. It was relatively cheap too, $41 from the UK for a rim brake "trekking" model T670. These aren't generally sold in the US for some reason.

So another question. I just built the rear with new spokes/nipples/rim/tape. Is there any reason to replace any of it? I've been on the bike maybe 5 times since I did it. I was going to do the whole thing in-place, removing the tension, taking a spoke out, putting it in the new hub in the same position and loosely attaching it back to the rim. Is that possible, or will there not be enough play? I've heard about replacing rims this way, but not hubs. I could take the freehub mech off the old hub to make more room too, but I'd leave the new hub intact. No sense in messing with something new.