1000 Islands NY to Burlington VT

The ferry certainly can accommodate your vehicle; they carry tractor traile trucks. I don't know offhand what the price would be, but it's quite possibly the quickest and easiest way; either that or the Grand Isle ferry (from right around Plattsburg).

Sticking to roads, you get to choose between two bridges that are more or less equally far removed from Burlington: either from Rouses Point, NY, at the northern end of Lake Champlain, and thence either along US2 or over to US7 or I89; or else south at Chimney Point, then following VT 17 to VT 22A to US7 north to Burlington. The northern one is almost certainly more direct than the southern one for you. Any of these routes is reasonable for a motorhome. There is some bridge construction along US 2 which might cause some delays coming down that way from the Rouses Point bridge.

The Cumberland Head Ferry is certainly the way to go. Most of the commercial cargo between VT and Plattsburgh uses it. You'll probably fall into the bus category on the following rate schedule. One of the ferries has an 11'3" height restriction.

Champlain Adult Campground just on the Vermont side is great place to stay for a few days.

Ferry

I-81 North to the Watertown Exit for US-11 to Rouses Point across The bridge to Vermont. Rte. 2 through the Islands to Burlington is a lot more scenic if your not in a hurry!

I-81 North to the Watertown exit to Rte 3 to Plattsburgh then North on I-87 to US 11 to the Bridge to Vermont if your a Leaf Peeper!