I had both knees replaced at the same time 5 years ago. Done in the afternoon, they had me up and walking at 8 the next morning.Out of the hospital in 3 days.
Home therapy for a month, then drove to rehab 3 times a week. Do the rehab, it is painful, but if you don't you will never walk correctly. The worst part is the knee bending for range of motion. They must do this to break up the scar tissue.
I took 1 1/2 10-325 percocet before they bent my knees back, and they could still hear me scream a mile away.
Be sure to get a surgeon that has done hundreds if not thousands of knee replacements and have it done at a hospital that has a joint replacement ward.
Artificial knees are not as good as the ones God gave us, but they are not bad at all. If you are in good shape, have them both done at the same time. There is only one recovery period. You should be able to walk around the house without help in a few days. You will need a high rise toilet seat to be able to get on and off the toilet for a few months. Also elevate the bed so that you can slip off to standing. I slept in an elevated recliner and could just rock forward to standing. After a couple of months, you won't need them. Stairs will need to be climbed and descended one step at a time , or with a handrail for 6 months to a year.
I know many others that have knee replacements. Everybody is different, I am about the average. None are not happy with their new knees.
I agree with all the advice given above.
Don't worry about it, The knees and doctors are much better than a few years ago.