Hello and welcome to the forum, Mike. Talk about a roller coaster ride in a whirlwind, getting news like that and so little time to think would put anyone into a panic.
First, I definitely concur with Sara Anne to seek out a second opinion hopefully at a major hospital that specializes in kidney/bladder cancer. I know time is of utmost importance when dealing with any cancer, but it seems to be rushed that your doctor has already planned out a surgery while still waiting on your complete test reports. Maybe he is very familiar with your case having treated you for this long, but even if you are already at a large hospital, unless they are on the list of top 10, I would still seek that second opinion. I think that applies to any major illness.
As far as seeing an oncologist, many bladder/kidney cancer specialists and surgeons are urological oncologists, and your doctor may be as well. If not, then definitely get that second opinion by someone who is. (I was treated at Vanderbilt in Nashville and most of their urology faculty are.) Since your tumor is between the kidney and bladder, I would want a second doctor to confirm that taking the kindey and a portion of the bladder is the best option. The experience of your doctor is very important to getting the best outcome.
It's tough being the family problem solver and being hit with something like this that knocks you for a loop. I know you don't want to frighten your family, but they will be your core support team along with your doctor. As soon as you can wrap your head around all this, I suggest you bring them into the discussion. It is a scary situation for all of you, but it is less scary when you have each other to lean on.
Please post any other questions as they pop into your head. There are so many things to think about when you first get that diagnosis. Many of us here have been right where you are and we're still here posting in this forum because we understand the fear and uncertainty. You will get through this!