VSL doesn't have cross fading. This is well discussed and you can search it out on this forum. Dynamics (p,mp, mf, f, etc) are assigned to specific velocity levels. In your sequencer, you can assign a region (term used in both Logic and DP), also called "object" or "part" in other programs, to a specific velocity level.
If you have any VSL Gigastudio library, using the current version of EmulatorX with Giga import, you can set up cross fading. But in Vienna Instruments, it's a work around.
I suggest you review some of the excellent demos by Jay Bacal, including his version of "Thomas Tallis" by Ralph Vaughn Williams. Here, you can download both the MP3 and MIDI file, which can be imported into your sequencer. You should then examine how Jay sets up the Volume, Expression, and how he edits with Expression.
This should help answer some of your questions.