I’m the resident Great Lakes wreck obsessed diver. I only dive the Great Lakes (or one of the quarries). I’m in the Chicago area. I did this thread last year that should answer a lot of your questions.
Great Lakes diving for beginners
Your best bet is the Double Action Dive Charters boat out of Hammond. Nice 16 diver boat that was new this year. Lots of good wrecks 60ft and shallower that are good for newbies. You can book per seat on the Double Action boats, which is not the norm on the Great Lakes. They also have a boat out of Sanilac, MI, and Milwaukee. Awesome wrecks but those are deeper and you need a bit more experience to do them. I’m a regular on the Hammond boat, usually every weekend.
Don’t even think about doing Lake Michigan in anything but a 7mm minimum. I’ve seen warm water vacation divers attempt it in a 3mm, but they came up shivering. It didn’t help they had little body fat!
If you’ve never dived a 7mm before, take one for a spin or two at your local quarry or even a swimming pool. Get used to the feel off all that neoprene, including hood and gloves, plus dial in your weighting. The big lake is NOT the place for that.
The season goes from late April to mid-October, but high winds/waves often cancel trips until about mid-May and from mid-October. Pretty much a crap shoot sometimes. My routine is the quarry from when t eh open in early April until I can get on the lake and then usually all of October at the quarry, and whenever we get blown out.
Let me know when you’re ready to hit the lake and I’d be happy to introduce you to my beloved wrecks.