Old ACL Injury

I partially tore my ACL in my left knee about 20 years ago playing hockey. The only sports I play now are curling and golf. I have been experiencing much pain in my lower quad muscle for some time. Recently had an MRI, revealed complete tear of the ACL. My surgeon said it has probably been torn for some time. He has manipulated my knee and said it is not particularly loose.He said I am in “the gray area”. I am 42 years old and I have bow legs. I have a custom made ACL brace. My questions are as follows:
Is my quad pain due to the ACL injury? Should I have the surgery done? If I do, what exercises or training can be done before surgery to facilitate my recover? ( I don’t experience much pain lifting weights, and I have full range of motion). If I choose not to have surgery, a) what are the consequences b) what excercises can I do to alleviate pressure and pain on my leg. Thanks.