I just wanted to respond, but Las Caletas isn't a resort (or in JA) but I would think things are fairly the same.
1. Will we meet the minister prior to the ceremony?
I did not meet our minister until after I walked down the aisle. Will met him on the boat on the way to the ceremony. He literally whispered "nice to meet you" when I got to the alter/table.
2. Can we specify what we want minister to say?
Ours had his own format of what he says. We were in contact via email before then and he shared what he would say and gave us the chance to change it. We liked his style and kept it as it was. He did ask for names of the person giving the bride away and other stuff he would have to say.
3. How 'easy' is it to add readings, sand ceremonies, etc?
Very easy for us. Via email he presented us with options of things to add - sand ceremony, hand blessing, gold coins, etc. He asked us to tell him what else we wanted and he would add it in.
4. Can we say whatever vows we want?
We did, and he didn't need them in advance for anything. In fact, if you recall I didn't even write mine until just before the ceremony!
I would ask your WC if there is an email addy for your minister so that you can get a little clarity.