I would raise the SG to about 1.024 as thats a good region to be in for marine. But that can be raised over time with water changes (increase the SG in the new water). As for introducing the rock simply place it in but make sure its cured rock . If you wanna save the small critters you can do lots of water changes to not kill them off, but i found it makes the cycle better and most life comes back alive.
Cured Live rock is basically, the rock is put in a tank and left for a few weeks to let dead inhabitants die off from its journey from importers. So that when you put it in your tank it doesnt cause a huge ammonia spike or a whole new tank cycle. You buy it from LFS or online its usually standard every where.