HUSSAR

You should read this:
 
http://www.avsim.com/topic/475671-01oct15-prepar3d-v2v3-compatible-installers-available/
 
and 
 
http://www.avsim.com/topic/476102-07oct15-some-bits-and-pieces-of-what-is-cooking/
 
There are installers for v3 but you will have to delete the NGX from v2.5, you cannot have duel installers.  Of course they will help if you have issues, it is PMDG afterall.

AVSIM has its own extremely popular library:
 
http://library.avsim.net/index.php
 
Avsim.su is in no way associated with this AVSIM.

James, you can access your extended download via your PMDG account, it expires after a year.  
 
Do yourself a favor and use an external HD or USB stick to save your installers onto and you'll never have to worry about extended download or the hassle of having to re-download your purchases.

Haven't used FSINN in a long time but I do recall having some issues with it.  I think FSINN loads a module while FSX is running and also shows as one of the processes but does not always unload when FSX exits so that's most likely why you were getting the error when FSX was exiting.
 
As for the UIAutomationcore.DLL, I think you can download the proper version from the AVSIM CTD Guide.

You don't say?  I have been wanting to get up to Whistler to ski for years, been there a few times during the summer but haven't been brave enough to face the slopes.  I hope you have a great time.
 
You probably already know about the FSX Scenery Config Editor to make moving of your sceneries easier, just in case you do not here is a link:
 
http://sourceforge.net/projects/fs-sceditor/files/latest/download
 
You can raise or lower scenery priorities much simpler (and safe) using the "List" tab.  And the beauty of this editor is that it automatically checks for scenery errors.  Be sure to make a backup of your main scenery.cfg before you make any changes.  FSX has 3 Scenery.cfg's, the main one is located in C:\ProgramData\Microsoft\FSX
 
All the best,
 
Robert