You can usually tell a bath and a half Newell from the windows. In the very rear of the coach on the passenger side if there is a small window it's probably a 1-1/2 bath. My '98 doesn't have that window and is a mid walk through bath.
Oh and there are a few mid-entry Newells with a window in the door. Just not very common. Like Clarke said they are all custom built.
Yes they are heavy, we full-time in a 45' 2 slide 1998 and carry more than we probably should. We still have about 1000# carrying capacity and a 10,000# towing capacity.
Newells are built to a different standard than most other motorhomes.
The best way to tell the year is from the front end design. Like others said check out newellgurus.com there is quite a bit of info there.