Attach the bush hog to the tractor and mow the cornfield, if there are still corn stalks standing. Detach the bush hog and attach the harrow to the tractor. Go over the mowed field with the harrow to rake up the corn stalks.
Detach the harrow and attach the box blade. Run the box blade over the cornfield to dig and rake up the corn stalk roots. Discard the corn stalks in an appropriate manner. If you are in an area that permits burning, you can burn the stalks, but if not, take them to the dump.
Test the soil with the soil test kit --- follow the instructions for the brand you purchased. Purchase the appropriate fertilizer, lime or other ingredient pursuant to the test results. Attach the spreader to the tractor, then spread the required amount of product to "repair" the soil. Attach the tiller to the tractor and till the ingredients into the soil. Allow the soil to sit for two to four months --- preferably over winter, if possible.
Till the soil once more, then smooth it out with the box blade. Spread the grass seed with the spreader. Using the harrow, rake the seeds into the soil. The follow the instructions on the grass seed you purchased --- but most seeds need to be covered with about a quarer-inch of soil to germinate.
Water seeded area gently with the sprinkler, following the instructions on the grass seed you purchased. Most seed recommends that you water early in the morning and again after the sun goes down, until the seed sprouts, then watering with an inch of water early in the morning until the seed becomes well established.