RE: How long for live rock that sat outside?
Test for ammonia. When its 0 its OK to put back in the tank. You may also want to take a tooth brush and scrub the dead stuff off of it while its curing. That stuff is called "Liver".
You might want to go to the GARF website and order some "Grunge" when it goes back into the tank. It will help re-seed your LR.
If you are starting over from scratch, just cure the rock in the tank. Did you salvage any critters?
Gary
125 SPS, 75 gal. LPS/softie reef, 9 gal. Nano