He has enough time in the Philly branch of the WCO so he understands the terminology and the concepts are all very similar. Just a matter of putting new labels on some stuff.
Protections now might be entirely different. I am not sure what the Rams do vs Philly in that regard, but he's seasoned enough in experience to where having a couple weeks to get protections down should be sufficient. If Stafford can't go for a while then I would think each game the protections would get easier but I wouldn't think they'd be a big problem. You're probably talking an extra sack or lost down here or there when he doesn't make his reads correctly.
Most of this comes down to where his head is at and whether he is willing to take correction and do the work. There's been all sorts of rumors about him having prickly pride and not taking coaching, not sure how true that stuff is but McVay will dispose of him quickly if he can't handle correction. But this represents a good shot at them trying to upgrade the backup spot which all I can say is it's about time.