Changing air dryer

Do you mean the air conditioning dryer at the front driver's side of the engine compartment. To replace the dryer the air conditioning system needs to have its charge evacuated using special equipment that will remove the refrigerant, store it and allow a vacuum to remain in the system that will allow the system to be checked for leaks. If a leak is found the leak must be repaired prior to replacing any other air conditioning components. The system is then recharged with the correct amount of refrigerant and correct lubricant and pressures on the high and low side are monitored with pressure gauges. This is not a job to be done at home.