Hi Dan,
My suggestion is that you pick up Route 91 South at the tip of Vermont. This will take you all the way down to about 75 miles from NYC. It's the best way from Montreal. The ride through Vermont and half-way through Massachusetts will be a relaxing drive. Traffic picks up around Holyoke, MA and thereafter. Tolls don't start until you get to the south side of Connecticut. Route 91 south turns into Route 95 once you get near the New York State line. From there, you will end up in a maze of exits, depending where you want to go. Rt. 495 takes you through the Lincoln Tunnel right into the heart of the City. (Manhattan)
I have a few suggestions for you...
1. If you have EZ-Pass (direct toll billing) put it in your vehicle. This will save a huge hassle at the tolls, and there are plenty. Some kinda pricey. Some bridges charge tolls in only one direction. Others, both.
2. If you do not have an EZ-Pass device, plan on about $50 in USD for the tolls. (both ways) If you blow through a toll, no worries, they will bill you. My daughter (who lives there) says they are direct billing at a lot of Toll plaza's now.
3. A good GPS is definitely your friend in NYC. Even the locals get lost... Sometimes your GPS get's lost too! Ha! Blame it on the tall buildings...
4. Never double park. It gets really expensive if you do that. Parking is expensive enough.
5. Make sure the vehicle you take is in top shape. The roads in NYC can be pretty rough in places. Be sure your spare tire is good.
Outside of that, have a good time
Regards, Bob