If the spell has any mandatory additional costs, those must be paid to cast it
Diaconis released a response indicating that you only need four shuffles for un-suited games such as blackjack
As useful as strengthening your board is, however, Priest of the Crossing has so much more potential in a sacrifice-themed shell
The set will also feature Garland, Knight of Cornelia and his alternate form, Chaos, the Endless
Also keep in mind that if you successfully import a deck, you may still need to make sure you've selected the proper format (if you import a Timeless deck but set it as a Standard deck, you'll get an Invalid Deck error message)
There are some sweet new gems to consider too, like War of the Last Alliance to go find some legendary creatures in the deck, and Tale of Tinviel to help protect a creature and get a creature back from your graveyard