Bowed wood floors can be a sign of high humidity, probably coming from underneath. Do you have a basement or a crawl space?
In each case, I recommend you to detect and eliminate the moisture source, otherwise the problem will be coming back.
About finding a good contractor in Michigan, the attorney general's website has great information, tips and resources:
At the State's Dept of Labor and Economic Growth, you can verify your contractor's business reputation and license information, by typing in his state license number:
Hope it helps.