Been diagnosed with an ovarian tumour. its 13x7cm big. what is the operation procedure like? is there a possible fatality element?

Depends : Usually in someone your age an enlarged ovary is a large cyst or sometimes a dermoid tumor. These is not dangerous. But still they involve a surgery. There are various techniques to remove it. Always there is a small risk of something more serious like cancer. This makes getting the surgery more important. The risk of mortality with this kind of surgery usually is very low. Talk to your gyn.