Well, if the pulsar cluster is anything to go by, you just carefully pull the needles over the little stopper things, and they go downa little bit more and stop, and you then mark on the cluster housing where the needle overhangs. Then you get a lever, like a really wide fork thing with 2 prongs and lever the needle off.
Then you simply unscrew the facia thing off (matty painted his, ask him how to to take that off on the micras) and then the original plastic guage pieces should just unclip or unscrew off.
Thats for a pulsar though so i cant be certain it works for a micra.
If you have some dodgey guages, like i know that the micra guages tend to get sticky over time and need re-greasing, take it to an auto electrician and get them regreased and while he does that, get a scan of the original guage backing things.
I'm still researching it though, I might experiment with an LX cluster without tacho.