no reverse not slipping just wont go into reverse its a inline 6 motor

What is your question?

few days ago if you gave it a little gas it would go into reverse gear good with no slipping at all but then a dealership drove it and floored it hard and since then the reverse wont work at all. how can we replace the reverse on the value body without replacing the whole thing which is $1000.00 for just the valve body part, no labor. Nissan doesn't sell anything but the whole body.