Sorry to hear about your Dad's situation. My Dad had the same thing happen last year. My Dad is 83 and he broke his hip and had a partial hip replacement the year before. He developed severe pain and they decided to put in the socket replacement part as well. But when they went in, they found that the stem was infected and had to remove everything and put in the spacer with antibiotics. They also put him on IV antibiotics. He did not do very well after the surgery - couldn't eat anything for a week - and stayed in the hospital for about 10 days.
He then spent the next 6 weeks in a nursing home rehab facility where he got the IV antibiotics and PT twice a day. At first he couldn't do much at PT. But they eventually were able to get him to use a walker with partial weight bearing on the leg with the spacer. I'm sure there are lots of variations in exactly what they put in for the spacer. I was told that they fashioned a spacer ball out of bone cement, so he could put some weight on the hip. After the IV ended, he came home for a few weeks. They arranged for a hospital bed at home and some home health care assistance (Medicare doesn't pay for the custodial care unfortunately) to help my mother take care of him. He had to be off the antibiotics for about 3 weeks before they did the tests to determine that the infection had cleared. It was almost 3 months from the surgery where they found the infection until the surgery where they put in the full revision hip replacement. In my father's case, he had lost so much bone from the earlier surgeries as well as from osteoporosis, that they had to put in a plate and wrapped wires around his femur to hold it together.
After the surgery, he was very restricted on weight bearing for 6 weeks, so he had to go back to a nursing home rehab facility. His scar extends well down his leg - maybe 18 inches. I know it was a very long and mentally depressing process for my Dad, but from everything I've read the two stage revision is the Gold Standard procedure for dealing with an infection. My Dad is home now and able to walk with a cane, but he is still very weak from not being able to use his legs for so long. He also still complains of some pain, but he is also diabetic and they suspect diabetic neuropathy may be contributing to that.
Good Luck - the hardest thing for us was to try to keep up my Dad's spirits when he was stuck in the nursing home. He was much happier when he got to go home. So if your Dad can go home with at home nursing care and PT, that would be great. Of course it really depends on how well he can get around.
Doug