twotone - cleaning is the important part [BrakeKleen is best], be very sparing with any lube inside the speedo assembly - at most use a small amount of white grease on the spiral gears that run the odo
Movinon - if your odo doesn't work and the speedo is 'sticky' it's likely the spiral gear that drives the odo is stripped or gummed up - see the tech tip to understand what happens inside - it'd be a good idea to disconnect the cable until you get it fixed to avoid damaging something further
Bill