Type of procedure is a big key. If it is the anterior approach he should do just fine. Posterior or Lateral it can be a different story. The hip replacement itself is not a problem, the muscles that get cut during the procedure determine recovery and rehab.
I had a total hip replacement last April anterior approach. Surgery 7:00 am, walking 10:30 am, home 5 pm and my life changed instantly. Pain was gone, mobility and range of motion increased dramatically. I actually went back to work the day after surgery, I felt better than I had in years. Almost a year later I can say it has been a life changer, I feel like a young man again, happier, more active. I wish the best for your dad. If I could offer him any advice it would be the same as my surgeon gave me. Trust the hip and use it!