GMC Sierra A/C Blows Hot and Cold Air?

My 2004 GMC Sierra 1500 2WD 5.3L V6 A/C blows but only on the driver side vents.
Ok, I have more than one problem, and both may be connected, but here goes nothing. I will explain this the best way I know how.

Problem #1:
Roughly 6 months or so ago, I noticed a noise that I can only describe as grinding, underneath the dash of the passenger side, near the floorboard of the truck. It would make the noise, at first, for anywhere from 30 seconds to a few minutes after cranking the truck. After so long, the only way you could get it to stop was by turning the A/C all the way up and letting it run, and hopefully it would stop. At one point, a few months down the road, it would only make the noise sporadically, which leads to the second problem.

Problem #2:
After the 6 months or so of the wonky noise, I cranked my truck one day, the noise started, and was really loud, louder than normal, and the air started to blow, both sets of vents, but then within seconds went hot. I tried turning the truck off, and restarting it, and it didn't work. I had to go to town that day, and went into a store, and by the time I came back out, roughly 45 minutes to an hour later, when I cranked the truck, the air blew cold again. Fast track another month down the road, truck was still randomly making the noise, and one day after making it, while my husband was in it, when I cranked it up, of course, the noise started, and the driver's side started to blow cold, like normal, and his instantly went hot. Ever since then, which has been about 2 months now, the only cold air I get is on the driver's side. We had to cover the passenger side vents due to constant radiating heat pouring from the vents instead of cold air.

So, here's my question, taking into consideration, all events that have occurred, what does it sound like needs to be replaced, or fixed? We're not rich, but my husband knows his way, mechanically, around vehicles, and with a little insight, we would be able to save a whole lot more money, not to mention, I don't trust too many people to work on my truck. Any info, help, or insight is thoroughly appreciated.

Thanks in advance.