anjaq,
I am a diver. I had FFS last February and went diving one month later. Depending on the procedures you get, your rest period may be longer or even shorter. When you can equalize your middle ears and all the bony work has regrown, then it should be fine to take a dive.
The most involved procedure I had was the forehead reshaping. My surgeon is Dr Mardirossian in Jupiter, Florida. He uses a technique where the frontal bone is removed in one piece, reshaped and replaced and fixed in place with small titanium plates and screws. The bone grows back in just a few weeks and then you are good to go.