I'm not sure what the differences were from version 3.0 to version 4.0. You could certainly install that version, or review the .pdf manual to get a feel for it. I think you'll find that the documentation is pretty sparse.

You asked about modifying factory styles. That's MUCH easier in Style Composer. To edit them in a DAW, you would first have to convert the factory styles to MIDI, and I'm not sure whether any version of the Style Converter program is capable of that.