It's pretty easy to do. I'm assuming that the ST185 cluster is similar to the SW20 cluster...Figured I'd take some pictures since my old cluster is sitting around unused.
The SW20 cluster is made up of 3 main pieces. Clear cover, Black centre section (gauge surrounds etc) and white rear section (connectors/lights etc)
The 3 sections are held together by a series of clips. What you want to do involves removing the centre (black) section of the cluster. So unclip it from the rear section. Then the black and clear section should come apart together revealing the white section and the faces
Removing the clear cover alone won't expose the actual gauge faces.
After that it's easy. Needles just pull off (be careful) and the gauge faces are held in by some clear glue like substance but they also just pull off.
Be very careful doing this. The stuff in there is very delicate and is very easy to break...
End result: Speedo face and needle removed. Putting them back together is straightforward
