Well, it sounds to me like you have the two lousy things about Jeep heating going on at the same time. If there's cold air blowing out of the passenger side dash when the eat is on, then the blend door is broken. They were poorly made and routinely blow out when you start the car with the fan on full. It's a pain in the butt to get under there and I had the dealer replace mine for $800+. Ridiculous but we use our truck to go skiing and we needed heat.
The seat heater, particularly on the driver's side because it gets used more, isa common failure. Chrysler used a seat design that has a metal rod running across the wires that feed the seat heater element. Jump in and out of the truck a couple of hundred times and the rod wears through the insulation and the whole thing shorts out. The current replacement item runs a little over $300 and requires pulling the seat, stripping the cover, replacing the element, replacing the cover. It's a bit of a pain, but not the worst thing I've had to repair.