Compressing piano-Help

[hitwriter]

I am using Digi 001, and I am running my kurzweil k2500 module through the channels. I am trying to get a good grasp on compression. I have read a lot, but still something has not clicked properly, because I'ms still confused.
When I play the piano, it picks a lot. I quickly go into the red ( which is a big no-no in digital recording, because there is no extra headroom right?)

1) Just to be sure, is the highest the maximum headroom available in digital recording 0 db?
2) Please explain the gain knob on compressors, I notice when I increase gain, it makes the whole db settings for the track accordingly. Should I increase gain or leave it alone.
3) What is the proper threshold level for piano, How do you determine where to set the threshold level on a compressor.
4) What are some settings those use to compress piano, so it sounds natural, but does not clip.

[mixsit]

First off, don't use the compressor for peak protection. Lower the record level. (-5 or 6 on a peak meter is fine.) Now you can start playing with the compressor for the sound of it. Get the instrument in the mix. Then come back with the question, what do you need the compression to accomplish?
Wayne