Thanks everyone for the info.
Sounds like an easy fix. Tapping the side of tank with wooden handle doesn't seem like an option. A small wooden building structure was built around the oil tank. They left a 2x2' removable panel at top of tank location, but no other way to access the tank, no other entry? Only way to access tank would be to crawl through this top panel opening. If I got in, don't know I could get out? Go figure ! Hey, I didn't build this arrangment.... Crazy setup !
Not sure if oil gauge is screwed in with double nuts, or a adapter ring screwed into tank. Will have to go back and check.
Good web-link I found which answers many oil tank questions:
http://www.inspectapedia.com/oiltank...ank_Gauges.htm
Bigdog