First, are you actually in the USA? Because that's what flag is showing, but the phrasing of your question suggests you're in the UK. If you are in the UK, then I know you're talking about lawn grass and not bermuda or other grass.
I'm afraid there's no easy way round this, particularly if you want to reseed. You can't just kill off the whole lawn and then reseed on top, it won't grow, seed (and turf) needs a good inch or three of friable soil in which to grow, not a solid mat of dead turf. You need to skim off the existing turf, then dig out any persistent and particularly perennial weed roots, completely, dig over the area, level and walk all over it on your heels to get out soft spots, then rake over and re level again. Only now are you nearly ready to sow seed - but you need to wait at least a week between the final levelling and actually sowing the seed, to allow the ground to settle. The same process is required for returfing - the difference is cost, and that turf can be walked on within a day or so, lightly, and used normally within 8 weeks, unlike a seeded lawn, which will be three months before normal use.

If that sounds like too much work, examine the turf you've got closely. If its more than 60 percent weed, then it'll have to go - if its less, then what weeds are present? Consider regular applications during the growing season of Verdone 2, along with a lawn food and mosskiller if necessary, and do the autumn maintenance this year (scarifying, cutting, aerating) and apply an autumn lawn preparation.