I know how confusing this is to you right now --it's still confusing to me, even after having gone through it! First of all, I need to say that there is no right or wrong answer, so don't go beating yourself up (now or in the future) about not making the right decision. It's a really tough call. It helps if your mother has a strong opinion about any of this -- but if she's like my mother, she will just let you take over for her and you'll have to figure it all out yourself.
My mother really HATED the idea of chemo, but she got so depressed, thinking she wasn't fighting and was just resigning herself to death, that eventually she felt like she should do SOMETHING -so we agreed that she could start the chemo on a sort of trial basis, and if she had bad effects, she could stop it at any time. This idea might work for your mom if you're unsure of how the chemo will work for her.
The chemo my mother had was Gemzar and Xeloda and after her first session she felt 100 times worse for a week. Then she seemed to bounce back and was feeling wonderful for a week, and we thought the chemo might have been working so we went for another round. That second round really depleted her, but we'll never know if the chemo wrecked her immune system or her advanced disease was beyong helping. Of course, others have had MUCH more positive experiences - my mother was always very sensitive to drugs, had many drug allergies and a compromised immune system from autoimmune hepatitis, so you have to take your mother's overall health into consideration. My mother was 64 and healthy but the hepatitis issue complicated things.
You might also want to consider some natural and alternative therapies that many people on this board have tried with some success. Change or restriction of diet, natural supplements, etc. Look under the "Alternative Treatments" heading and you'll find a wealth of information. But if your mother is averse to trying any of these, don't push too hard (thinking of my mother again, and how she'd never give up her coffee and donuts, and how could I bug her about those small joys in her life?) There are also clinical trials that you can look into. Oh, and make sure you ask about getting some prescription nausea meds if she doesn't already have some, and meds for other symptoms like indigestion, pain, etc.
As for getting the best doctors, I do believe that it's important to get an oncologist who has a lot of prior experience with cc, as it's still considered rare and many doctors don't know what to do. More important than anything, though, is finding a doctor who is sympathetic and helpful and informative - someone you can really talk to. Too bad Sloan Kettering won't take your mother's insurance, but Mount Sinai is also considered pretty good in general (not sure about their experience with cc, though) and you may find a great doctor there. Don't be afraid to switch to another doc if you don't like this one. As for the docs in Florida making it seem like it doesn't matter what oncologist she has, well, they could be right -- but they could be very wrong, so I'd see that she got the best care that her insurance allows.
Is your mother feeling relatively okay (any symptoms?) and recuperating well? I hope they don't suggest chemo until she's fully recovered and up to it. How is she handling this mentally? And how are YOU holding up? I wish I had gone to a support group or grief counseling while my mother was still alive, but I suppose it's hard to find time for that when you're taking care of a loved one. But please find a friend to vent to -- or feel free to vent to me! This burden takes a lot out of you and is so painful to go through. I wish you a much better outcome than my mother had - and it IS possible. I don't want to take away any hope with my depressing story. I just want to help others going through this in any way I can. It's a tremendous blow when you get this diagnosis, and your mother may be very understandably depressed. Just by being there with her and taking care of her, you are doing the most wonderful thing in the world, and I know she appreciates it. I wish you and your mom all the luck in the world.
PS - To add to my very long post, just a thought: if your mother doesn't want any chemo, you should look into hospice services in the area. They are invaluable resources and offer medications for comfort, psychological counseling, medical supplies, and lots of information for those who decide to forgo treatment.