TSB: 'Downeast' means as far to the northeast in the continental United States as you can go...albeit it is a northeast direction from where you sit. Look at a map of Maine or the US and make a pinprick at the extreme upper right corner where New Brunswick, Canada meets the USA. For those who haven't ever visited that part of the US, you are in for a treat. Beautiful rocky shores, and although you can't see Ireland for there, it lets you know where you are looking. Cool ocean air in the summer....damned cool ocean air in the' winta'! Bob in Ft Kent sends down ice cubes on the hot days in July, and don't forget, you are at a border point with a foreign nation, so bring the passport if you want to come back stateside.
I would not worry about installing the unit to your existing boiler, it is a simple operation that can be all drawn up so that you have the materials on site before you start. Plenty of advice available on the forum, so welcome to the world of those who burn without creosote.
Goggle 'Calais, ME' look upward (North) on the map and you will see Limestone Air base that was closed many years back(Houlton, ME). Look upward more and you will see FT Kent! Now you have some degree of measure when Bob says it's -41 this AM, just where he lives.