Please keep in mind that anything you do in the spring that involves new grass seed will give you a yard full of crabgrass all summer. The reason is that crabgrass seed needs exactly the same conditions that you would give new grass seed (bare soil, sunlight, and continual water). You can minimize crabgrass by growing your grass up as high as the mower will let it grow and by minimizing your watering once any new grass is established. Then next fall, once the summer heat breaks, reseed again to fill in where the crabgrass tried to take over. Fall is the best time to reseed because you don't get the ugly weeds and you can establish a nice dense turf. So even if you get a lot of crabgrass, don't worry. It can be fixed without Herculean effort.

If you decide to dig out the sprinklers, just do it with the same tractor as you will hire to regrade. It should be a tractor, not a skid steer or a bobcat. The attachment he will use is a box blade with rippers.

If you decide to just fill, then you can do that yourself. Keep a bucket of sand or topsoil with you when you mow. Use a broom to sweep the dirt or sand down into the turf so the grass is not covered. You can easily smother your grass with too much. Again, tall grass helps.

If you are worried about your soil, you might look into an organic program. All the reasons not to try organics are pretty much gone. It is about the same cost as synthetic fertilizers, does not smell bad, and will not kill your grass. Furthermore you don't have to live with weeds, and even if you want to use a weed killer, you can minimize damage to the soil by spraying each weed rather than dumping dry chemicals on the soil.