Cancer should be covered under medical insurance. Biopsies are a medical procedure and covered by medical as well. It depends on how things get coded,

I would advise you to see an ENT who specializes in treating oral cancer patients. You do not want the kind of ENT who primarily puts tube in childrens ears. Oral surgeons dont always treat oral cancer patients. Many treat a wide variety of things like TMJ, wisdom teeth removals, etc, If you havent already been seen by an oncologist that should be one of your first steps. When being treated at a comprehensive cancer center, a team based approach is used with all the doctors meeting together at a "tumor board meeting". Together they will create an individual treatment plan for each case, That should be done prior to setting up for surgery. You will want to know what the big picture is specifically for you, and what is the best way to eliminate your cancer.