2002 Prius Voltage Leak and shut down

Hi
I have a problem with my 2002 Prius when I was driving down the highway the master warning light came on with a warning display screen appearing saying that there is an problem in the Hybrid System and then car went into shut down mode. I had it towed to the dealer for diagnosis and a estimate. The codes read were P3000, P3004, P3125, and P3009 they did not tell me the sub-codes read. There diagnosis was the inverter needed be replaced. The Main battery on this car had been replaces at 140,000 and there has not been a problem since, the car has been well taken care of throughout its life. Being new to working on hybrids but not cars and electronics I figured I could replace it cheaper than the dealer price of $4200. With the age of the car and high miles 175,000 I figured it would not be worth the new part price so I got a guaranteed used inverter. After replacing the inverter I still got the same problem with no change So I decided I would have to diagnose it myself. The car starts and runs fine and starts charging the battery right away as normal but if try to but it in reverse or drive it fails so that means the short would have to be in the transaxle. I decided to test MG1 and MG2 for shorts and I figured I would need to use a megger to do this but I did not all three winding on MG2 test shorted to ground on the 200 ohm scale on a regular ohm meter. Then after closer inspection of MG2 cables you can see a coating of corrosion running up all three cables. So the question I have is this corrosion on the cables a common problem for 1st gen and could it be possibly just a cable issue and not MG2 and can the cables be replaced without dropping the engine and transaxle???