almost all of my farmland is already tiled, but there is about 300 acres that could use tile in between the existing lines since they are 80 to 90 foot spacings. What equipment would I need to buy to do it myself, and what would it cost? I have a 4WD 350 Hp tractor to pull a plow, and have a good backhoe. Most of my land has 2 to 4 % slope, so do I need a laser? TIA.