I'm dealing with the same issue. On my way to Rosemont I glanced at the speedo and was shocked to see I was running 135 @ 2200 RPM.
Below is a link to a guy who repairs them for $169 ($189 for the entire cluster) including shipping BOTH WAYS!
In the mean time there's a 'reset' proceedure you can do. Turn on the ignition and click the key forward just shy of engaging the starter. Each time you do this the speedo needle will work its way back toward zero. It may take five to twenty clicks depending on where the needle sits. Mine works correctly for days, then out of the blue it goes nuts again. And most recently, it worked its way back to zero on its own! Go figure.
And FWIW, my local dealer told me I'm looking at $600 to $800 for
them to do the fix.
Go
here.