Not much for manuals out there. I posted one awhile back I got with my 800 that came from the original owner. Let me check later, I almost think I found a 400/600 manual too at some point.
The 400 is the easiest one to find in the wild, and really the best for a good resto project. My 400 is currently in parts in line at my sandblaster to get cleaned up before re assembly.
You will be in it over 500 with just the baffle and grid. If you can, try and give Buck a call directly, and he is always cannibalizing old Cawleys that are not allowed in that part if the country, for parts for people.
And most important, since your in NH, and if this project gets pushed back and you want out, give me first chance at making a deal with ya for the stove