In November 2004, my wife and I are flying, on a business trip, from
Southern California to Palm Beach, Florida.

What recommendations do you have in regard to airline(s), ticket
costs, minimum stop overs, minimum aircraft changes in route, with the
following information:

From:
Ontario Airport (CA) to West Palm Beach, Florida.
(Our first choice)
Or:
Los Angeles International Airport (CA) to West Palm Beach, Florida.
(Our second choice)

Two senior adults:
Round trip:
We would like to fly first class, or with an airline that has ample
seating and leg room:
Leave on a Wednesday, and return the next Sunday (Total of 4 days and 5 nights):
Cost is a factor, but not the controlling factor: 
Ample seating and leg room is preferred:

The main reason I am posting this question, is because of possible
aircraft changes and uncomfortable seating to the West Palm Beach
airport.

I do not believe any airline flies direct from LA to WPB, but you can
easily get there with one change of planes on large aircraft.  For
examples, you could try for Continental with a layover in Houston,
USAirways with a layover in Charlotte, American with a layover in
Dallas, or Delta with a layover in Atlanta.