There's going to be a lot of different answers to your questions because of the nebulous term "reseal". I'd suggest to make the dealer explain what they are going to do. In fact, that is a good strategy with any service being done on anything.
Most dealers are going to go on the roof and apply new caulk over the old. Dicor sealants can be treated in this manner. You can't just put any sealant on the EPDM roof. It needs to be one that adheres, has longevity, and won't interact badly with the rubber membrane