My DB has has both of his hips replaced. He was only 32 at the time of the first hip. Due to fears/concerns he put off that surgery for some time. He talked to everyone he knew who had the sugery - or had a family member who had (as you are doing).
Prior to surgery your father will be told of EVERYTHING that could possibly go wrong. Yes, there are some VERY serious possibilities, but he will also be told the odds. (I drove DB to this appointment. It scared me more than him.) Face it, there are risks anytime one has surgery.
Even immediately post-op DB was in SO much less pain. He kicked himself for putting off the operation for so long. When it came time for the next hip, he had the operation right away.
His surgery was in the morning, the hospital/MD had him on his feet that afternoon. He had to be able to go up/down stairs in PT before he was released from the hospital (even if the house doesn't have stairs).
He wasn't allowed to sit upright for 6 months. It's been about 16 years, so I don't remember the details, but it was several increments up to 90º.
I just remember the 90º taking 6 mo. because DH and I took my DB & SIL to WDW as soon as he could sit upright for the plane trip. He needed to have some fun and my SIL is a SAINT for putting up with him. She needed to be able to relax, so DH pushed the wheelchair (his Surgeon required him to use the wheelchair for the trip, due to the amount of walking involved).
As this was his first trip 'handicaped', he was nervous. Being only 32, he was afraid of how he was going to be treated (people thinking he was 'abusing' the system or CM rolling eyes at having to deal with another wheelchair). WDW came through with flying colors.
Oh, DS has pointed out to me some people that kind of 'roll' as they walk. This is due to hip replacement.
Best of luck to you and your father -