Actually, Christopher, I'm not misinformed. I did err in referencing the unaired pilot, but the character descriptions are genuine. They're from the original Gilligan's Island treatment. The characters had changed after this first iteration and were on their second go-around when the pilot was filmed, as you stated above. The characters changed again, iteration three, into how we know them today.
There is a series of shorts called Gilligan's Island: Before the Three Hour Tour which detail the following:
The Professor was originally a writer.
The Howells were not millionaires.
Ginger was a secretary, and Bunny was a store clerk.
Gilligan was a Navy cook who knew nothing about the sea. He lied about his background to get the job aboard the Minnow, as the Skipper's regular first mate had crapped out.