Jon,
How long you would be off work kind of depends on what they have to do when they remove the bladder.
You might want to consider subcontracting to someone or hiring someone on a temporary basis to fill in to keep the business going while you recover. I'm guessing you could direct someone and do final inspections easily enough after a few weeks (but I wouldn't be doing any torque wrench activities for a while).
I had a neobladder operation done and the doc said no travel for a while. I'm a business consultant usually traveling Mon-Fri every week and home on weekends. I spent a month or so working from home after being in the hospital for 12 days due to a complication after my surgery.
You should probably plan on 6-8 weeks minimum, but your mileage may vary. For strenuous activity, it would be even longer.
Best of luck!
Mike