Sorry that your Dad didn't get to use his Airstream more. You can post it for sale in the Classifed Section of these Forums. As stated above, you should post a LOT of pictures. You will need to take these pictures with a digital camera at the lowest pixel setting. This they will post without you having to go back and reduce the file size.
As far as pricing goes, go on Ebay under AIRSTREAM to get an idea what the going prices are. Remember that a vintage Airstream's value is based more on its condition than on its model year.
Maybe a Forums member in your area will see this posting and be willing to come by and take a look at your Airstream. This person can assist you in testing your Airstream's systems (electric, water, sewage, ac/heat, appliances, etc.). You must have this information for potential buyers unless you are willing to let it go for a give-away price.
SuEllyn & Brian McCabe
WBCCI #3628 -- AIR #14872 -- TAC #FL-7
2015 FC 25' FB (Lucy) with HAHA
2005 Suburban 2500 Quadrasteer (Olivia) & 2011 Silverado 3500 (Fred) with Outfitter Truck Camper (Ethel)