Well it has been a while, but I should have entered the final findings for this especific issue once it was repaired.

It turns out that none of the components listed above that the dealer proposed replacing were the problem. The issue was resolved by repairing two (2) wires that were routed from the the Pulse module (located left engine compartment behind fuse box) to the ECM module on the right side of the engine compartment. Once these two wires were repaired verything started to work perfectly, to include RPM gage, Airconditioner, battery, etc.

Thanks