Ron,
No help on a gunsmith in Chicago, but I can give a thumbs up to the Springfield shop if you decide to use them. I also had the shooting low thing (we must have got our TRPs around the same time) and sent it back to them instead of filing on the tritium sight. They had it back to me with a new front sight within a week. Don't know if they still have the same quick turnaround, but work was done well.
Otherwise you might check one of the Chino Valley, AZ 1911 smiths. It seems a boatload of them moved down there some years back, so there's quite a few top notch guys to choose from. The wait might be kinda long though. I used Don Williams after Ted Yost turned me down because he was too busy (he recommended Williams), and Don had the gun I sent him for around 8 months or so.
If you decide to go to Springfield and you do the swap for Professional parts, if I'm not being too nosy, I'd be interested to hear what they're charging for that.