Bill,
There is a comparable model Cessna 150E (1965) on eBay right now, with a "Buy-it-Now" price of $22,450.
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=280577705421&viewitem=That is your competition, and you can watch it to see what it sells for. While both your and the eBay planes are very clean, the market is very depressed right now. Older Cessna 150s will most likely sell to a private buyer for a sport plane, rather than a flight school wanting a training or rental aircraft.
I have always had a fondness for the 1965 square tail- it just looks so cool!
