Hello,
Let's assume that you have a sensor on the rear axle that is failing. Replacing it isn't quite as difficult as it is on the front axle

.
Remove the old sensor from the wheel bearing housing .
'Forcing it out somehow' would probably be a more accurate description.
I had to really force mine out because they were stuck in the bore. Afterwards, I used a Dremel or something similar to grind away the rust from the bore, and possibly used a magnet to 'suck up' any metal shavings near the toothed ring. Then, I installed the new one. Without grinding, the new one would be very difficult to insert and remove, and I was afraid of damaging the new sensor during installation, so I preferred to grind everything away.
But, in my opinion, half an hour is not enough.