Fwiw went through a similar sort of thing at the start of the year. X-rays found what appeared to be something nasty on my lung and no other test managed to contradict it so I had an operation to remove a lung. Fortunately the surgeon had decided to only remove the suspect part initially, go for a coffee while they test it and then finish the job if it was really dodgy. Fortunately he didn’t need to so I only lost a part of the lung.
Obviously not nearly as serious as what you are going for but what I find is that my heart rate rises much faster than before when I push it so I have to take care and watch what is going on. If I don’t then I definitely get out of breath on big climbs and it’s easy to push it to a point where I am in trouble. I tend to pay attention to what I am doing now rather than going as hard as possible.
Going through it all I found at least one person I knew who had had a lung removed a long time ago and I would never have guessed.
On another note I found it hugely helpful to look up a lot about the operation in advance. You wake up with a shitload of cables and tubes connected but if you know in advance that is going to happen and what they all are it really removes a lot of the stress (or at least it did for me)
Good luck, especially with the preparation and getting your head round it. And of course you will need a new bike to help 😉