I am so sorry to read this about your Sydney.
Having just gone through this type of experience with our RB Thumper it's NOT an easy journey. Any good vet surgeon will tell you, surgery can actually make growths come back even bigger once they are taken out.
We opted NOT to have surgery. Her story is under "cat health" Thumper.
Be prepared for the emotional ride of your life. I will keep good thoughts and prayers for your Sydney.