likely what they would do is re-bake the header at the normal 2500 or whatever degrees and that burns off everything down to bare metal including the ceramic and just recoat it how you want.
the coating youre thinking on is 'ceramikrome' and it does shine very similar to chrome. and you are right it will NOT discolor due to heat up to about 1800 degrees, it can chip and if it does then moisture seeps into the metal becaus ethe seal has been broken and rust starts. i should show you a pic of my ceramic header right now after a NY winter

uzzled::nervous:

aranoid: