I'm in the NW Suburbs (Schaumburg). Exactly what suburb are you in?
As the others said, if you apply ANY weed killer, pesticide, etc. you need a license.
Here is the website for more info:
Very inexpensive to take the training classes and tests (2 full days-$40 total).
It is extremely helpful to use the "Search" function on this site. The questions you asked have been discussed quite a bit. Don't believe everything you read on this site, once in a while you may get some bad info, but 90% is usually accurate. Also you are dealing with cool season grasses. The people from lower Illinois and south have very different growing conditions and different grasses.