Don't know where in Vermont you will be staying, but someone mentioned Burlington? As mentioned before, best to figure 2 days from federal lock in Troy NY to Lake Champlain. Then 1 day to Burlington makes a comfortable trip.
There are 2 marinas in Whitehall NY just north of lock 12. You can also tie up to the wall overnight just south of lock 12 and walk to town.
Also, as stated above, the NY State Canal Corp has info.
Several marinas on Lake Champlain. If you are staying in Burlington around July 4 you should call the Burlington Boathouse at 802 865 3377 when they open around May 1st to make reservations. They fill up fast at that time of year
Also The Lake Champlain Atlas of Navagational Charts (order on line) is a good way to go for charts. The lake is well buoyed. The buoy system was originally set up for tugs pushing gasoline and fuel barges so a couple of buoys are not critical for our size boats. But without local knowledge one should respect them ALL, as some are very critical. For instance 90 feet of water on one side and 2 feet with stumps on the "wrong" side.
As of last year the very best gas price on the lake was at Buoy 39 Marina on the Vermont side about one mile south of Fort Ticonderoga on the NY side of the lake.
The name is from the since renumbered buoy system. The marina is at green can #73.
Speaking of buoy numbers, be aware that the reds and greens change sides after you leave the Hudson River
Buoy 39 has only 22 - 25 boats. We keep RONJO there. If you do stop there ask John or Cindy if Ron & Doris are around.
Good luck.
Ron PS Obviously-it is Burlington-kind of late last night and wasn't paying attention to what I was reading(LOL)