Re: Leveling out yard
If you want a golf course smooth lawn, then I'd just rototil what you have - no spraying, level it, compact it with a roller, and then seed or sod the area. If all you want to do is fill in the holes, then get yourself a couple yards of compost or a topsoil mix from a landscape supply and simply fill in the holes. You can layer in the fill and let the grass grow up through the fill before adding more fill, or you can fill the holes to capacity and seed over the top.
I personally disagree that you have to kill the grass before filling the holes completely, the grass is going to do one of two things, die and compost or grow up through the fill, either way, no big deal. The only reason I'd kill the grass first, is if it is an unwanted variety, basically a weed, then I'd kill it, fill it and seed it.
I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!