The default Extract Faces command does split those faces into a separate mesh, it just puts the resulting faces into component mode right off the bat with a manipulator function similar to the "Transform Component" tool. After running an Extract, just tap F8 to get back to object mode. It's clunky, but works :)
I like to put the quick keys for selection hiding and unhiding on my shelf. It makes it really fast and easy. Having delete history, freeze transformations, center pivot, and flip normals is really helpful as well. I use isolate selection a little bit, but it is only active in that one view port, the functions I showed…
Modify -> Center Pivot will move the pivot to the bounding box center of your mesh. Group are extremely handy because you can transform multiple objects at once using a new pivot (the group's pivot) while each individual object retains it's on object space pivot. Hierarchies are your friends. I'm not quite understanding…
I'm guessing you're coming from Max? In Maya people use groups alot more, usually you want to organise your scenes with lots of groups, which makes the outliner quite useful. Ctrl-g (create group from selected objects) p (parent objects to last selected object/group) and shift-p (ungroup selected objects) are all your…