| Re: Help! Dodgy Gears.
Wheel truing's actually very very easy with the right tools! I used to work in the Edinburgh Bike Co-Op and one of the guys managed to build a full wheel in his lunch hour! The hard part with wheels is calculating spoke length, then working out your spoke lacing pattern.
One very quick fix you can use to get your gears sorted is using the barrel adjusters on the rear mech and the shifter. Basically, if your gears are slipping from low to high (big cogs to wee cogs), you need more tension in the cable, so you need to turn the barrel adjuster so that it moves away from the shifter, and do the same on the rear mech's adjuster. This is the most likely problem, due to the gear cable naturally stretching, and also the cable sliding in the rear mech's grip bolt. Basically keep turning them til the slipping stops. If you adjust them too far, your chain will start slipping the other way. Basically, you're trying to use the cable to line the mech up with the cog you want.
If you've moved the barrel adjusters to their maximum extents and it's still slipping the way it used to, your next best bet would be to screw the barrel adjusters back in as far as they'll go, then undo the bolt on your rear mech that holds the cable in, but not completely. What you'll need to do is hold the cable end in a pair of pliers and just loosen the bolt a wee bit so you can pull the cable through. Pull maybe about an extra centimetre of cable through from its original position, then re-do the bolt and try using the barrel adjusters to fine tune.
But hey, like everyone's saying, any bike shop should do it for super cheap, most bikey-minded people could sort that out in a few minutes. | 
