Here is my background highlighted and what I did:
Not cancer for me but in Sept 2015 I was diagnosed with multiple sclerosis which is the worst thing a Dr. has told me. I was 33 at the time, just gone PT from FT in my career because I was bored and topped out in my field and had jumped into a PA program to change career fields. MS doesn't kill you, but it takes your life away at some point. Most people within 10 years of diagnosis can't work and something like 50% of people will need daily home aid around the 15 year mark. My last relapse had taken part of my vision, I couldn't remember my wife's name sometimes, forgot the best way to drive home from work, and could no longer handle the impacts of mountain biking, trail running, or carry a pack very long for hiking. There was no way I was going to pass PA school and even if I did wasn't really a smart move at that point. The financial impact of MS is brutal, I read one statistic that it was the 2nd costliest long term medical condition to have. My insurance was paying something like $5k per month for Tecfidera (I was only out $35 per month due to pharmacy agreements Blue Cross had) To face those numbers put a knot in my stomach and tossed more questions out there than I could answer, many of the same questions you have as well. End of life considerations? Where will the money come from? Bucket list? Job security? You get the point since your likely asking the same questions.
What did this diagnosis change for me and how did I change? Every aspect of my life is different. And many for the better. I spent 8+ hours a day researching MS and various options to fully understand down to the cellular level what was going on. Read peer reviewed papers so I could talk on a more clinical level with my Dr.s, and new exactly what the drugs that I was taking were going to be doing to me. Having MS is sometimes a crap shoot on what works, it's a very unique disease and what works great for one person doesn't work at all for another. I dropped out of the PA program and went back FT with my employer to ensure I maintained cash flow. I completely turned into a FIRE mindset and aggressively started saving. From a medical stand point I went for a nuclear option and had an autologous HSCT performed (in broad terms heavy chemo and a bone marrow transplant using your own cells) to essentially create a new immune system (MS is an autoimmune disease). It is still in clinical trials here in the US that I didn't get into so I went to Europe and had the same thing done over there and paid 100% out of pocket. That was scary as hell in its own right laying in a foreign country hospital bed with no immune system. I still save, aggressively now. My debts are mostly paid off or will be soon. I am building a home that is a one level ranch so if my MS gets to a point I can't use stairs the home will be easily turned into a more accessible home. My health is much more stable since treatment, I still have MS but the treatment is designed to put it into a very long term remission. I don't smoke my weekly cigar, eat a really health diet, and have met some great people over the last couple years I wouldn't have without an MS Dx. I just got back from 8 days in Glacier National Park and hiked every day. I live my life accepting what I can change and what I can't. I don't too often get stressed (really bad for MS), and have worked hard to mold my life to be as positive of a person as possible.
Control what you can, research every option possible. Ask questions of your medical team, whether comfortable questions or not.
Don't feel the need to hide your emotions or feel the need to put a brave face on. Cancer sucks and your human, lean on your friends and family. If your frustrated, talk about it.
Keep cool about the finance options, the future is uncertain for 100% of the human population. Keep your plan in place as best as possible and handle the issues as they come up.
Talk to the hospital/insurance/etc... about options if things get tight.
I wish you the best of luck, I know a couple people that have gone through skin cancer and are doing very well. One of them had it on their jaw. After the removal and some very minor plastic surgery you can't really tell there is a scar.