I am refinishing my french oak desk.  The old finish was coming off and discoloring due to sunlight after a dozen years.  It is time.  The wood has a lot of detail, curls, some knots, black markings.  I assume the original finisher used some filler to highlight some of the old markings.  I want to try to match the original color/look to the greatest extent reasonable; i also want a durable finish.  This is a desk.
 

1) Should i use a sander filler (de-waxed shellac)?
2) dye versus stain for oak?
3) What clear coat would you recommend – lacquer, poly, something else?

Here are pictures of before (the matching bookcase) and a few shots of the legs and underside of the desk.