To end the story (for now at least), I went to the local auto parts store and bought some AC Pro Professional Formula Refrigerant with Gauge and Hose (20 oz.). I followed the instructions (which were pretty clear) and filled up to the “green” settings. it was on low (very low) and now we feel air out of both vents. I did not need to change the blend door actuator (at least not for now). Thankyou for clarifying the fact that it is possible to have no cold air blowing on one side with simply a lack of refrigerant. I had assumed that wasn’t the issue because I assumed that it would blow cold on both sides automatically if there was refrigerant. At least I know how to change the actuator if I ever need to do that. By the way, for any novices out there (and I’m a big time novice), it is pretty obvious to tell whether the actuator was working in hindsight.