it is definetly possible to do drawings in SU that incroporae structural detail, like the layers of dry wall you mention, but it does take some preactice.
As for the 2x4s, i'd recommend making a generic one and turning it into a group (select the faces you want to group>right click>group) You can then copy it around your model and then scale it to fit (scale tool.)
Layers do work, although in my experience i've found them harder to use than in programs that are more layer orientated, such as ps. It just takes some getting used to really.
I think what you really need to do is start a bit smaller and work your way up, it is pretty hard to learn the finer details of sketchup on a big model, as your too busy concentrating on the model as a whole. Try and have fun as well!
oh and welcome to the forum, and good luck with your model.