Joe, there is a lot posted on this at www.Citristrip.com but here't the process for bleaching. First, strip the piece of all clear finish. In a location that is not easily visible, like up on the inside of the modesty panel, test to see what works, bleach or oxalic acid. First, wipe a sponge or rag soaked with regular household bleach on a small area. Give it a few minutes to work and then neutralize it with one cup of white vinegar to a gallon of water also applied with a clean rag or sponge. Let this dry and you will see if it has removed the color. You may not be able to see this on wet wood.
If it has not, go through the same process using a product called Wood Bleach that is actually oxalic acid and is sold at home centers under that name. Follow the label directions including neutralizing.
Now you will know which product works so you can proceed on the whole piece. With the age of the stain and finish on your desk, you should not run into the same potential problems as with the cabinets that were the subject of the original post. Since you will have used products containing water on your desk though, the next step in finishing is to lightly sand with 220 grit paper to remove any raised grain before restaining. Use a sanding block whereever possible.
My old desk was stained with Minwax Red Oak stain over a spit coat (5 parts denatured alcohol to 1 part white shellac) and I am really happy with it.