Yes, gypsy moth caterpillars can attack maples, as well as hundreds of other tree species. You've raised a number of other issues here and leaf diseases such as anthracnose and tar spot have been prevalent after what was a wet spring in much of Michigan. Trees under stress for any reason are more likely to be attacked by insects and/or disease, or both. Leaf fungal diseases, while they can make the tree look ugly, generally do threaten long term tree health. Gypsy moth caterpillars are out now and you can read more here:   https://www.canr.msu.edu/news/gypsy-moth-outbreaks-in-michigan

You may well have other issues going on in your tree as well. Anthracnose has been documented numerously this spring. Read more here:   https://ag.umass.edu/landscape/fact-sheets/maple-anthracnose 

Tar spot as well:   https://www.canr.msu.edu/news/black_polka_dots_on_maple_tar_spot

The professional to contact when all of the above become too much for you is a 
Certified Arborist, one who specializes in these matters.  Find one or more Certified Arborists in your zip code at www.treesaregood.org  Go to the Find an Arborist tab. Arborist evaluations are not expensive and where you can learn exactly what is going on in your tree.   

Good luck!