I have a 99 pontiac montana with automatic transmission with 89000 miles. It shifts very rough and jerky in first two gears. Worst when it warms up. I was told that the problem was an internal valve body failure and that it needed a PCC, solenoid, filter and gaskets and valve body as well as a transmission flush. What should parts and labor cost to repair it? Is it worthwhile to repair or buy a rebuilt transmission?