Re: Speedometer Issue
The only thing I can think of is to take the cluster back out and verify all of the connections.
It sounds like either things weren't re-connected quite right, or, the system shorted damaging the cluster during the work you were doing since the battery wasn't disconnected. Since the gauges only get power in the run and start positions, I would check to make sure power is getting to the unit when it is supposed to (The odometer is on a separate circuit to allow it to come on when you open the door...I think...)
You could also try to pull codes. Many of the inputs to the cluster are monitored and a problem may trip a DTC and point you in the right direction.
Apart from those things, I think the next step would be to test gauges directly using a scantool to ensure proper operation of the cluster itself.
Hopefully it is something real simple.