Echoing what GS34 said. Strength training is really important the older we get. I have found that it is the key to virtually all the aches, pains, tendonitis, etc. associated with age. I haven't had the hip replacement, but I had back surgery. After following the rehab program the surgeon and physical therapist recommended, I still had significant problems. So, I took the program into my own hands and put together a strengthening program to complement the stretching, etc. they recommended. The results were unbelieveable and I'm pain free.
You and your body know what's best.
Good luck!!!!!