I expect that the speedometer problem is completely independent of any other problem you have with your instrument cluster. There are two common speedometer problems, one would be the speedometer cable causing the needle to bounce around, if this is the case fix the speedometer cable. The second is the odometer not working. This is usually the trip odometer binding. Either way consider the speedometer and the rest of the instrument cluster as two seperate items that happened to be attached to each other. It is very easy to remove and replace the speedometer from/to the cluster, once the cluster is out.
Your other problems could be a loose connector, or if limited to the temp guage could be the sender in the engine.
Give some more specific descriptions, and I'm sure we can help you. It is a ten minute job to remove the entire instrument cluster and have it ready to lay on the workbench. We can help you with that too.
Give more specific information regarding the nature of your problems.
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