Frost will kill crabgrass. Don't apply the pre-emergent until next year.
Here are the first and last frost dates for Joplin Mo.
http://www.victoryseeds.com/frost/mo.html
You don't sound like you have a lot of experience. If you are not licensed get it, and read a few hundred posts on here and you will soon be aware of the fundamentals. And be sure you are actually looking at crabgrass--not quackgrass, nutsedge, orchard grass or something else.