No reason to email the hotel in advance. Just mention at check-in that you have a separate reservation for an add. night and the check-in agent will make sure you are in the same room. I have done this several times and no issues encountered. The following morning you stop by at front desk to have your key cards updated based on the second reservation.
I'm quite sure that you will have to pay 2x USD 46 for parking when staying 2 nights