oral cancer- any adivse to help my bff

My best friend Eine a Golden Retrever and I went to the vet on Tues, for a lump in his mouth on his gums. She told me maybe oral cancer but didnt say it could be anything else? We go in next tuesday for surgery to remove the cauiflower looking lump. She says she going to caterize or burn the surrounding tissue to try and kill off any cancer if it had spread. She also said that she would run a blood test to check his liver and kidneys,I didnt understand when she said that then but I do know. I learned on-line that a cancer called melanosarcoma can spread to those areas. If she runs the test and it's already spread should I go through with the surgery? If anyone has gone through cancer with there best friend Im asking that you please respond to this tread. Im lost,scared and broken hearted. Eine is my best friend my love and my life. I cant sleep,eat and its so hard to got to work because i feel like im loosing presious time from Enie. Please help my best friend and me.

Einie weighs 84.5 lbs
He turns 6yrs. memorial wkd
Ive had him since he was 8 wks old.
other health problems: Hot spots