Maybe you guys have had to do this. Customer wants entire lawn redone. Its only about 6,000 sq./ft. However it is made up of 80% weeds. I think its got every possible weed in it. Crabgrass and broad-leaf weeds. I've heard to just kill off the entire yard, but I am not too familiar with what would be the most effective route or the best time to do this. I know I will have to slit seed and fertilize the lawn a couple of weeks after doing so. Any advice would be greatly appreciated.