Hopefully getting the compressor replaced tomorrow on my AC unit. When replacing the compressor does all of the refrigerant need to be replaced as well? The evaporator coil was replaced in January and thought they put it new refrigerant then and didn't want to double up in the same calendar year if it is not necessary.

They will have to evacuate and recover the existing refrigerant. If I were you, I'd want a clean fill anyway. R410a is relatively cheap compared to R22, so it shouldn't break the bank. If they are replacing the entire condensor unit it's also likely that the new unit will come pre-charged with enough refrigerant for up to a certain length of line.