Wait until late summer to kill and redo it. It's as easy as glyphosate/Round Up two weeks prior to seeding, cutting as low as you can with your mower (preferably bagging the clippings) and throwing out seed and lightly raking it in. Grading a lawn is another story. Unless we're talking a thousand square feet or less, you're gonna have a miserable time of it without at least a lawn tractor. It can be done, but not easily and not inexpensively. If it's only slightly bumpy then "grading" isn't necessary. You can use hand tools to fill in low spots with a mix of sand and compost (the more compost, the more the bumps will come back).