I use a Nissan pathfinder 2000. Recently it has delay engagement of the transmission from neutral to drive and will not move unless it is changed to gear 1, then it moves perfectly. Then I manually change to gear 2 before I change to drive. At the drive now it moves and changes easily with the torque. I took the it to a transmission shop. They did a fluid and filter replacement. But no improvement. They were suggesting I change the valve body. Kindly assist. Thanks
If they changed the fluid and filter and there is no improvement then they are probably correct - get the valve unit changed.
Trying to clean it and refurbish that valve unit yourself may not be very successful, so having it replaced is likely the best option.
You say the vehicle is from 2000, how many miles has it done? It may be more cost effective to get a refurbished or remanufactured transmission complete with guarantee...