I just found out I most probably have stage 3 peritoneal primary cancer with a slim possiblity of it being lymphoma. Where should I go for the best?

Best is relative. The best is relative. What the best for a person does not have to be the best for you. Having a diagnosis of cancer, you would need to get some good support from friends and family to go through treatment etc. Also when economy is tough sometimes travelling to another states is not possible. My suggestion is to start with cancer ctr close by. Later, d/w your md re- 2nd opinion at tertiary center.
It depends/many. It depends where you are, but for the best, many places appear to be top notch. Memorial sloan kettering in new york is a great place since it deals primarilty with cancer. The mayo clinic and the national institutes of health are also excellent, as is cancer treatment centers of america, which is in many places. The american cancer society is a great resource for any cancer info.