Hey Luke, welcome to Scubaboard, and the rabbit hole of coldwater great lakes diving. Its a wonderful thing, but is significantly different from the diving you've done. I checked my logbook from last year, and the temps I had on the Maple Dawn and the Marquette were 68F. Toby is far colder, even when shallow. You will need a good 7mm suit minimum, hood, gloves, and boots, and possibly an added vest depending on conditions. It wont be fun if you're not comfortable. They say most people dive Toby wet........once. Its not actually true, but for what it's worth, we purchased drysuits after our first real season of diving locally.
We (my wife and I) do a mixture of group diving with a couple shops we frequent, and a bunch of walk-on charter stuff on our own. We dive primarily with Dan's Dive Shop out of St. Catharines, and also sometimes with Float and Flag in Burlington. Both shops have charters and local trips that would be of interest to you, and is an excellent way to get the feel of Coldwater. Dan's has weekly Wednesday night dives, but they're all in the Niagara region, so a bit far from you. I'm sure local shops must have similar events in your area. You almost need an LDS to get started diving here, based on the requirements for experience to get on the charters. It was with a shop trip (FnF) that we did our first diving in Toby. We had done our training with them (ow, aow) and were accompanied by instructors and DMs over the weekend. We also got to meet the staff @ Divers' Den, and they got to know us. That got us the required experience to be able to pursue the walk on charters on our own. We were coldwater from the get go, so not sure how warm water trained divers are handled. Maybe taking a course with Divers'Den would be the easiest and cheapest way to accomplish your "vetting", and get the experience.
When in Toby, we're in drysuits and this season we'll be diving double steels. We tend to focus primarily on the morning advanced charters which are reasonably deep and quite cold. My wife really has a thing for the Arabia.... and I love the Niagara II and Forest City. Not the best dives for someone starting out.
As for the equipment, you really have to decide if this is something that you are seriously going to pursue, as the cost of coldwater diving can be significant. You want to know you'll be diving frequently to justify spending the thousands of dollars it's going to cost to get setup properly. If we were renting everything all the time we wouldn't likely get out nearly as often, both from a cost perspective and also from convenience.
Anyway, I'm by no means an expert, but I'm happy to answer any questions I can regarding gear, Toby, etc...
Hope this helps a little, and best of luck.