You digest protein and your body breaks it down into amino acids and poly peptides. They are then absorbed and transported to the liver where they will either undergo gluconeogenesis or be released into the blood stream. Your tissues then take up the aminos that they need. The remainder is either converted to lipid or CHO intermediates by the liver and then either stored or released back into the blood.
You do not pee out excess protein, and fiber will not increase or decrease protein uptake. It may slow the digestion, but that's about it.
As for a protein shake prior to working out. I don't think it will make much of a difference. Now, having a liquid protein after you workout with some CHO will.