I'm getting married on June 9th in Punta Cana as well....my WC gave me the list of items I needed. They included pretty much what that poster above me has quoted:
Notarized Single Affidavit signed & translated, Passports translated, birth certificates translated and legalized, any divorce decrees or name change documents need to be translated as well.
We also had to send passport copies for our witnesses to our WC.
I live in DC, and there's a Dominican Consulate here....first they said they no longer do it, then they said they did, then they didn't again. I ended up using WeDo, who has to send the documents to the Dominican Consulate ANYWAY....
Hope this helps.