I am "cancer-free" but I am still on Herceptin (I am Her2+ and er/pr -). I will be on Herceptin for a long time - precautionary measures. I too hope it stays gone, thanks.
Regarding the surgery, that is tough. I never wanted the mastectomy. I actually had convinced the doctors to do another lumpectomy on the same breast (the cancer came back in the same breast), but then I told myself to just do the mastectomy because I did not want to worry about cancer every time I had a mammogram (those horrible people at the mammogram place would send me letters after my mammogram, "there was something suspicious with your films and you should follow-up with your doctor." I would freak out each time. (Insert angry face) I hate those people.). I chose to have the other breast done because I did not want a reminder of what I used to be / look like. I thought having both done would help me move forward and not stay in the past. With that said, I do regret having the second one done but only because they also had to remove the nipple. The doctor does inject something (some time of dermal filler) into the nipple area so that through a t-shirt it looks like a nipple, but it isn't. I am not sure if I would have made the same decision if I wasn't so upset and stressed out. The doctor told me to take all the time I needed, but I was so frazzled that I couldn't think and just wanted to be done. I would definitely ask about keeping your nipples. It is something to consider, it's part of your femininity and intimacy. My cancer was right behind the nipple area so she had to go. I don't remember the reason I was given for why the other one had to go. I am not even sure I was listening / heard it.
Side note 1 - that reminds me, make sure you are taking someone with you to your appointments or taking a note pad to write things done. What the doctor says and what you hear may not always match. Write down everything, even the mundane. Chemo brain is real. It will pass, eventually, but it is real and don't be afraid to say it to someone when you are having trouble remembering something - "I have chemo-brain ..." Mommy-brain is real and socially acceptable - chemo-brain is real and should also be socially acceptable.
Side note 2 - if your doctor hasn't mentioned it, ask about chemo-pause. Just be prepared that it may happen, it may not. Just ask if it hasn't been brought up.
Back to the surgery - Double check your insurance and see if you can get the other one done at a later date versus choosing now. I think your doctor's suggestion about doing the other breast - if you choose to do so - during the expander/implant exchange is a great option. It will give you time to think, check things out, see how you feel, etc.
Regarding the recovery. I have to say, it was not hard for me. That was the easiest part. With that said, I actually had an allergic reaction to Arnica (they gave it to me to help the swelling) and that was ugly. I was red and inflamed and etc. I was fine once we realized the problem. The only pain I felt was like the soreness after a chest workout. It was discomfort, but I did not take any pain medicine. I have heard others say the opposite, but for me, I was okay. I did walk a lot and made sure to eat healthy and stay hydrated.
You will probably have drains after the surgery to help rid your body of the extra fluid. Follow your doctor's orders and "drain your drains", keep a log and take care of the area. Oh, if the doctor wants you to sleep upright, get one of those back support pillows with an armrest, a bedrest pillow. I got mine from Bed, Bath, and Beyond. They are usually used for reading or watching TV in bed. https://www.bedbathandbeyond.com/store/s/bedrest-pillow?ta=typeahead&ml=v2
I don't know what state you are in, but contact your state American Cancer Society and ask your doctors for some local agencies. I have met some wonderful people and have been given great information - including on where to get some freebies. Our American Cancer Society gives free wigs and scarves and some other things. We have a great breast cancer resource center that does programs, runs support groups, does girls-night-outs, all kinds of fun things. It really helps.
I don't know remember if you said if you have kids, but Camp Kessem is a one or two week (?) sleep away summer camp for children with a parent diagnosed or who passed away from cancer. It's free and they have camps all over the country. My children did it but didn't like it, they said it made them sad. However, another person we know, and several of the kids at the camp, LOVE IT. They look forward to it and find it helpful. The camp does periodic get-togethers and really try to make it a family atmosphere.
Feel free to ask me anything. That's how I got and still get through it.