Haven't seen a gallstone/liver mets connnection. There are some stone dissolving drug options like ursodiol, depends on what kind of stones.
But i have been following the surgical options due to mom having some rattling around in there. I believe Murtha died in a laparoscopic g-bladder surgery. But he was kinda big and that seems to pose problems for less "open" approaches. They have some newer teeny tiny single incision approaches which I'm not sure are "mature" as they say.
Whatever the procedure, please review this and see what kind of anesthetic is involved:
Opiates/Opioids (accelerates cancer, remedies)
http://her2support.org/vbulletin/showthread.php?t=42074