You will also need to notify Harvey Watt and get a return to work letter from them...learned that one the hard way at the last minute.
As for vacation vs. reserve. Whatever R days are left over after your vacation knocks them out will constitute a mini-RLG. The comments about sitting at least one of those days are correct, otherwise your RSA account will be charged for the entire mini-RLG amount. If the amount of hours are 30+ (I think) then you can request DSA be applied instead.