OK , from reading your story I can imagine there could be one solution to offer even though we (Me & Robert) don't have FSX.
First things, first. Unistall the PMDG add-on. Then re-nsitall it.
Furthermore, if this is not a paid-for PMDG then there are problems with most of the editions out there. They usually mean that the main screens start operative but then go black and there's nothing you can do to bring them back to life. Only solution to this one: Get a different version.
Regarding switching from panel to panel, there's also a keyboard shortcut, in case you don't see the little 'panel selector' buttons. This is done by pressing "Shift" and one of the numerals on the top row of the keyboard (not the ones in the num-pad).
Try it out and you should find which shortcut opens which panel.
If all of these fail, then let me know what exactly happens and I'll scour the fora to find you something.