1987 Nomad AC Blowing cold then warm then cold

If your ac unit is 27 yrs old, it very well may be worn out. Being a sealed system, no freon should be leaking out. And if it is, what is to be done about it to prevent the new freon from leaking out. The Clean Air Act doesn't allow R22 Freon to be vented to the atmosphere. This may be a problem for a repair shop's heating and cooling tech to install a tap and risk a violation. I wouldn't risk my electrical license in such a manner as it would definitely harm my lively hood.