Hello there! I am 68 and just had TKA 9/13/23. I was in the same situation as you. Here you go:
1. How painful/hard to climb the outside stairs when I leave the hospital? I was not able to do stairs for about a month. At first one step at a time - surgical knee first, then the other. I worked at the PT facility on stairs - they had rails on both sides. After about 2 months I could go down normally but VERY slowly and with some difficulty. Now at 3 months - I am not quite as slow but being very careful. At home I have a rail on the left side (going down) and I hang on!
2. Would it be better to extend hospital stay to 2-3 days? I was allowed to stay one night in the hospital and then was ready to go home. IF you start PT right away - the day of the surgery actually, you will be fine.
3. How long before I should be able to navigate the outside stairs for rehab/walks/outings as a passenger? Use a cane if there is not a rail. Take it easy and don't be in a hurry. I still can't go for a long walk - but it is VERY cold here so my knee gets stiff.
4. How long before I can sleep upstairs in a bedroom (there’s a second bathroom upstairs). I would wait until you are VERY comfortable. Do you have a partner that can watch out for you? I had to use my walker to get to the bathroom at night.

The other advice I can give you - TAKE YOUR MEDS AS SCHEDULED. Stay on top of the pain. After two weeks I was able to stop the oxycodone but took it faithfully. You won't get addicted, if you are careful. I still take one Advil and one Tylenol every afternoon to take the edge off the pain - but as I said it is very cold here (Northern Idaho). ALSO take the peri-colace and eat prunes.

I developed restless leg syndrome about 3 weeks after surgery. Taking ropinirole (.5 mg twice a day) and it is helping.

I completely lost my appetite. Have some comfort foods around - instant mashed potatoes, toast and cheese - that sort of thing. My husband made me steak twice and it tasted awful to me. Lemon popsicles were great.

I still ice every afternoon for a couple of hours - I have an ice machine so I can't get frostbite. It is so comforting. Elevate as much as you can. And sleep sleep sleep. Your body needs the rest to heal. Don't feel guilty!

All the best to you - the pain was a scary thing for me. I am scheduled for my second surgery and am not at all fearful this time. You will get through it and be so happy you did it. Wishing you a very Happy and Merry Christmas.