Female in the late 20's. My mother died of stomach cancer in her 30's. Her brother is fine & parents lived till old. Should I get gene-tested?

Colon? When your mother had stomach cancer, do you mean colon cancer? Colon cancer does have a generic link and requires further testing. Lynch syndrome, hnpcc. Not aware of a genetic link to "stomach cancer". Worth discussion with your primary care.
I am not sure. If stomach cancer is hereditary. All cancers involve genes but not all cancers involve defective genes that are passed down. You may be a candidate for endoscopy to look inside the stomach. What would u do differently if it came back positive anyway, get stomach removed? Check if stomach cancer is hereditary, don't let yourself suffer from reflux and avoid risk factors; u may get better answer.