So, the left side rotary speedometer isn't working?
It's most likely just a bad connection. On the back of the gauge cluster, there are three connectors that probably need to be unplugged and re-seated (fairly common issue).
Your right side clock/oil gauge may be fixed by the above method, but most likely just has a bulb out (also replaceable from the rear of the cluster).
This article will show you how to remove the gauge cluster -
http://www.pelicanparts.com/techarticles/Boxster_Tech/90-ELEC-996_Cluster/90-ELEC-996_Cluster.htm