Buying it from a dealership is not worth the expense. All you need to do is to start looking for totaled 2016+ Fiestas; the part you are looking for - in online catalog - is under "Amplifiers", "Sony", 6.5" screen. But, I'd recommend you educate yourself on what's needed and whether you want to go with a NAV or non-NAV.
Use the search on this forum if you need more info - the part numbers could be found, but I would not obsess about it. The primary issue are the brackets - since the comm module (APIM) could ostensibly be sourced from a different model, like F150. However, given that you are looking to buy the whole thing, I'd suggest that you limit your search to Fiestas -then it will be a simple remove&replace job. About $350 altogether, based on the current prices.