Time off will depend on what type of hip replacement it is, ie. the type that uses cement to fix it or the one which has a serrated edge which the bone is left to grow around.
If the latter (which I have had for more than 20 years) I would suggest it would be about 6 months off, as you are not allowed to put ANY pressure on the leg for 3 months after the surgery, then the muscles are so weak you will need about 3 months of physiotherapy.
Once it's all over, though, there shouldn't (barring complications) be any problem with re-certification. The range of movement is checked every medical, that's all.