Any recommendations for a Marine Motor T Sgt. switching over to 11B? Things I need to be studying before I go to Benning?

Try grabbing a copy of FM 7-8. It's the infantryman's bible. You won't have to know it verbatim but it won't hurt to know the fundamentals of what you'll be doing and what the terminology is. Oh, and on that point, be prepared for a change from Marine lingo to Army lingo. I too made the switch from Marines to Army. No one will know what you mean by "the deck", "the bulkhead", "the head", etc. No one says "Aye, sir". Calling cadence in the Marines is waaaaay different than in the Army. The Army enunciates more where Marines just sort of grunt. Good luck to you.

Remember that the Army PT test and Marine PT test are different. No pull ups in the in Army, the pushup standard are almost identical, we do sit ups instead of crunches and while the run is only 2 mile instead of 3, it requires a substantially faster time (8 minute miles verses a +9 minute mile for a passing score in the under 21 category). Getting ahead on the Soldiers Creed and such is a plus.
Are you just doing Phase II?

The Soldier's Creed, the Infantryman's Creed, the General Orders (should be cake compared to the Marines' version), and if you really want to impress, the Ranger Creed.