Congrats on the new boat. You must be very excited.
We did the Downeast Loop in 2012, and our blog for the trip can be found starting here
https://www.mvtanglewood.com/2012/05/plan-complete-downeast-loop.html
There are three routes from Albany/Troy, NY to Quebec City. Have you sorted out which you want to take? With each of these routes it will be important to check the water draft, air draft, and possible boat length limits. Your boat will be one of, if not the biggest boat going through any of these routes. We were in a Grand Banks 47 and were one of the biggest boats we saw the whole time.
The three routes are:
1) Continue up the Hudson to the Champlain Canal, through Lake Champlain, then the Sorrel (I think that's the name) waterway to the St Lawrence. You enter the St Lawrence between Montreal and Quebec City, so will need to back track if you want to visit Montreal. The Champlain Canal has a low bridge of 17' or so and you will need to be sure you can get under it. I have only been through one of the Champlain lock, but all the lock on this route appear small and charming.
Both of the next routes you take the Erie Canal to the Oswego Canal into Lake Ontario. Then the routes diverge.
2) Take the St Lawrence straight out to the ocean. You will go through the Thousand Islands region which is very nice, but the rest of the way you will be going through the big commercial locks on the St Lawrence. We found them quite unpleasant. There is nothing charming about them or the surrounding areas. It's all business, and as a pleasure boat, you are the lowest priority for locking through. Assuming it still works the same way (but check), each morning the locks operations would publish lock times for pleasure boats. You need to then zip on over and tie up to wait for the time. But don't expect the schedule to hold. And changes in commercial operations will impact your schedule. You might go through right away, or you might wait 6 hours. All of this means that you need to stage each day close to the lock so you can make an early scheduled lock through, and you need to be prepared to stay the night not far downstream from the lock in case you can't lock through until late in the day. Because of all this, we did NOT take this route.
3) Go to Kingston, ON and take the Rideau up to Ottawa. First we did a couple day trip through the Thousand Island area and back so we didn't miss it. Then we went through the Rideau. This was an absolutely lovely trip, charming, low stress adventure. There are a lot of locks, but they are small and very pleasant to go through. And at the end you go down the Ottawa stair step locks. From there you follow the Ottawa River down to Montreal where it rejoins the St Lawrence. There is at least one huge lock along the Ottawa River, but it was not a hassle like the St Lawrence locks. With this route you only need to go through one of the big St Lawrence locks (or maybe it was two?) just as you reach Montreal. This route is longer, and the Rideau has a controlling depth of only 5'. We drew 3'10" and so I told everyone we drew 4', and at one spot I got scolded for not calling ahead since I was 4' or greater draft. I never did find that rule anywhere, but you might have too deep a draft for this route. But if you can fit through, I highly recommend it.
