I haven't had my gall bladder removed but on my initial CT scan before ileostomy surgery the report indicated that my "gall bladder was packed with gall stones". I asked my surgeon about this and he said that many people have gall stones in their gall bladder all their lives with no complications. Problems can occur when the stones become dislodged leading to blockages in the bile ducts (but there would be severe symptoms such as jaundice, severe nausea and pain, etc, to alert you to this and off to the doctor you would go).
I figured as they haven't given me any grief as yet (touch wood) will leave 'em alone, and I would prefer to keep as many organs intact as I can, given that I like you are colon free, plus the fact I have full intention of never entering a hospital ever again (as a patient) if I can help it!
But having said that apparently a cholecystectomy (technical term for gall bladder removal) is a very simple procedure, and I haven't heard of any major problems with people that have had them removed. Hopefully someone that has been through it all can give you more info.
As to prevention, plenty of water and hydration seems to be the general consensus (and steering clear of fatty foods), and this is always a good move with us ileostomates anyway.
Cheers my fellow Oz-tomate (just checked your profile!),