Go for it asap.
I had my hip replaced several years ago, brilliant result.
When my hip first played up I tried all sorts of things, pain relief, physio etc. Eventually it got beyond a joke and I was booked in to have it replaced. Shortly afterwards the cartilage collapsed completely and I spent 2 months in agony, should have had it done much earlier If the joint is worn out, it is not going to get any better, just worse.
I had my knee replaced as soon as they diagnosed terminal wear, even though I was not in too much pain, I knew it could only get worse.
You will be in for a few weeks discomfort, but within 6 months, you will have forgotten you have a replaced hip.
Bit suprised you have been told 6 months, I though 18 weeks was the maximum now, I only waited 3 months total from when I was referred.
I know Mishap has had a rough time with her hip, but that is unusual.