I'm afraid there's no simple way to get your Finale exported MusicXML to load VDL in Sibelius. Not sure where you saw there was a how-to for it, but I don't know of one. Anyway, the problem with trying to use imported MusicXML files in Sibelius is that you'd have to go in and manually tell Sibelius exactly what each sound should be, essentially building out those instrument definitions from scratch.
Your best bet is to start from a clean copy of the Template and input everything as if writing a new score (do not copy/paste anything from the other score as this will likely bring in unwanted/hidden elements). You may not have wanted to hear that, but it will be the quickest way.
And what exactly are the "newest" version numbers you're referring to?
I'm using Sibelius 8.0.1 running the OS X 10.9.5
I really don't want to manually input everything. If I were to buy Finale, would that make it easier to get VDL integrated? Could I then at least just copy and paste the score into the template, if not just integrate the template into the MUS file?