Congrats on your new to you purchase!
For the capacities, try looking at Newmar's
brochure archive. I looked and didn't find capacities in the 1997, but the Kountry Aire DP brochure for 1998 has capacities and the 4081 model may be close to your 4080. Also looking at coaches with a similar floor plan should help you determine the tank capacities.
Can't help you with owner's manual, however it never hurts to call Newmar. Also, take a look at their ComNet site, (PARTS INQUIRY" link at the bottom of
this page. The "TECHNICAL INFORMATION"
and "TRAINING" links have useful information regarding systems, and under "CATALOG - MODEL YEAR" the 1999 model year may have a coach with a similar floor plan (also you can access the brochures from 1999 on from here).