Hello all, I am about to completely re-level and re-seed my entire yard, front and back and pour a new driveway, which is now asfault and is sinking and cracking badly. The front yard is not level at all and the same with the back and side yards. The back yard has sunk due to, well I believe, the drain field from the septic tank. So what my plan is is to bring in fill dirt and level with a bobcat, my yard is 1/2 acre.

So my question is, do I need to kill or remove the existing grass? Is has many many many weeds and dandylions so I am not that worried about trying to save the existing grass. Or can I just spread and tamp fill dirt directly over the grass that is already there? I'm thinking I should just kill the grass, all of it, then spread dirt over and level that way, but not for sure?

But there is no sense of killing the grass if I have to remove the grass that I just killed... AM I over thinking this????

Any help will be greatly appreciated!!!