" I called Breitling SA to ask what a service would cost. They informed me that they would not work on the watch as it had been opened by me. "
Ridiculous, non sensical business practice. Yes it is concerning if someone unqualified opens a Breitling or similar watch, and it should void any warranties, but it should not disqualify it from ever being repaired. What on earth is that all about? If they think you might have done something damaging to it, they should offer to fix it as part of a service, not give you the cold shoulder.