It took three hidascans to catch my bad gall bladder. I had mine for 5 years. I was beginning to seriously think about raising enough money to pay for my surgery out of pocket without a diagnosis because I was so certain that was my problem.
I was 23 when I had mine out, so age certainly isn't a factor. But my mother had hers out and several other people in my family as well, so I think you're right about genetics.
The surgery is relatively easy; you'll be released to go home the same day. Afterwards it takes some adjustment because foods that might not have bothered you before will (temporarily) bother you now. I found that eating any meat other than chicken or fish would give me diarrhea. This lasted 4-6 weeks, then I got to where I could eat beef and pork again. Stay away from any foods that bothered you before as well. Basically, you need to be on a fairly light, somewhat bland (don't go without any spice, but Indian food and some Mexican will be too much) diet for a month or month and a half. Then you can start adding things back in. You may not be able to tolerate all of your old offenders--I still can't tolerate caffeine--but you should be able to handle most of them, albeit in small doses (I can handle three pieces of pizza, but no more).
If, after a month or so, you are still having problems with diarrhea, then see a G.I. and get a prescription of Welchol. A year after my gall bladder surgey I was still having random bouts of bile diarrhea, and when my G.I. gave me this, it stopped the diarrhea. Now all I have to do is avoid caffeine, go a bit light on the pizza and fried foods, and take a Welchol every day and I have pretty good bowel function. Better than I had before the gall bladder came out. And I don't have pain or nausea anymore either.
You may want to start on the Caltrate 600 w/vitamin D pills as soon as you experience diarrhea after your surgery to help lessen that effect. I have a theory that bile--being such a strong acid--causes irritation to the colon when you let too much of it go through there too long. I also think (and there are studies which seem to indicate this) that the calcium helps heal/soothe that irritation quickly. So, after so long with gut problems, that might be something you really want to try and take in order to get your guts better faster. Linda (Inape) says that's all she needs to treat her post-gall bladder problems. Sometimes I take calcium in addition to my Welchol because I need a little extra boost. But I have seen people on here who take as many as 6 Welchols a day, so there's no telling what level your guts might set themselves to. And some people (a much smaller percentage, I think) develop chronic constipation. I have found that a diet too low in fat will (at least for me) cause severe constipation, so if you do have that problem, try adding some good fats back into you diet. There's also supposedly an old-timey product called bile salts which help replicate the missing bile (which is the cause of the constipation) and they're supposed to help. Other laxatives like aloe vera, prune juice, fiber and/or magnesium will probably provide as much relief as you need.
And one other thing I have noticed: you pay for your indiscretions for about twice as long as you enjoy them. So if you eat your offender foods all day one day, you can expect to have a bad day tomorrow and probably a not-so-good day the day after that. A week's bad eating ends up costing you two weeks of irregular bowel movements, and so on. So when you start having problems, it's best to nip them in the bud by changing your food and/or changing your medicine (some things can't be helped, like a cold or antiobiotics getting you messed up; that's when you try and apply more gut medicine to compensate).