Auxiliary Clearance Surgery- help & advice

Hi, I've recently had a lumpectomy and unfortunately one of my lymph nodes had cancer cells in it. I've now been told I need an auxiliary clearance, which is frightening the hell out of me. I understand it's a big operation with 4 weeks recovery. I've read about lymphoedema, a potential side effect. I'm 54 and this has all come as a complete shock. I'm also unsure if this means the cancer has spread to other parts of my body and what comes next. Any advice would be gratefully received. Thank you