No dealership in the world is stupid enough to replace the entire ac unit, its not like your home split which comes in a box, its a very large collection of parts when it comes to your car and all carry their unique part numbers.
What you will get is factory repair schedule which is to do a pressure decay test to detect leaks in the system with nitrogen bottle and then do a vacuum decay test, once the repairs/replacements are done and both tests pass again, the system is charged with the correct weight of refrigerant.
Problem is that MG is almost nonexistant in pk and its service and maintenance mechanics maybe of questionable skill, this is why you should not choose to buy a product with no solid backup support,