Configuration, chirality I'm having trouble assigning priorities for this molecule:

I tried assigning priorities with the rules for doubly bonded atoms in mind. I know that the lowest priority group should be going into the page (not on a wedge) but I read that I can simply assign a priority with the fourth priority group on a wedge and then take the opposite of whatever I assigned as the true configuration of the molecule. Problem is, I get R. Answer key says S.
Your drawing is correct and yes, "I read that I can simply assign a priority with the fourth priority group on a wedge and then take the opposite of whatever I assigned" this is true too.  In your drawing 1->2->3 is a clockwise rotation (therefore "R" but), but the lowest priority item (4) is coming out towards you.  Therefor, the R/S assignment needs to be reversed (from "R") to "S".