I believe you are loading the Dictionary and not a single dialogue array, so you should use Call "Dialogue_StartDialogue" ("DictionaryKey") to call the correct dialogue.
You could indeed add a fade in effect, but once again, you might have to adapt the code a bit, depending on how you want the fade to behave. The simplest would be to add a fade in behavior to the 9-patch (window), SpriteFont and portait sprite, and be done with it. However, it might not quite be what you want. You could set the behavior disabled on start, and enable it conditionally on object creation. You could also delay the "typewriting" to occur by setting the "Dialogue_Timer" to an arbitrary value (most likely the fade in duration in ms) instead of 0 in the "Dialogue_StartSequence" function (event 10).
Don't be afraid to experiment, the system should be robust enough to work even though you fiddle a bit with it.