Good luck. Can't gain much fitness now. But recovery is important.
I'm also running Chicago and coming into it overtrained (finished last week at 92 and started missing workout paces). After a few days of rest I'm starting to feel better- yesterday was 15 x 500" @ 90" pace/45" rest + 40min @ 6:27. None of that has anything to do with marathon pace as I'm targeting <2:35 however it is good to be feeling good again.
As other said get some super shoes. Bring some gels for nutrition (I'd maybe max out at 2 gels if it's your first time) can be hard on your stomach. I wouldn't experiment with too many runs now bc you shouldn't really be doing long runs leading up that would put you in the same state.
Get a massage or something. That may also help the body recover.
And good luck. Find a pace group to run with and stick with them. Let them break the wind (if any).