I'm interested in optioning the film and video game rights to a
science fiction novel written in the 1940s. It's by a fairly
well-known science fiction writer who is deceased. The book was
previously adapted into a film in the 1950s. 

My question is three-fold:

1) Where should I begin my inquiries to see if the film rights are
available? I think the book is still in print in paperback. Should I
contact the paperback publisher, or the author's estate? If the
latter, how do I find contact info.

2) How will the fact that it was previously adapted into a film
complicate acquiring the rights?

3) What sort of price-ranges should I assume for the option and for
the pick-up price? 

Concrete precedents would be especially helpful. Some analogous
situations would be...

Jack Finney's "Invasion of the Body Snatchers" which was made into a
movie in the 50s and 70s and is currently in production for 2006.

Isaac Asimov's "I Robot" which was filmed in 1988 before the recent
Will Smith version.

Robert Heinlein's "Starship Troopers" (although that hadn't previously been filmed.

Some of the Raymond Chandler novels which were made into films in the
40s but haven't been filmed since.

I've done some reading already on Warren Adler's site, but am looking
for some more specific insight into the economics:
http://www.warrenadler.com/ask-movies.shtml