What can cause the dash to warn about the 4 wheel drive and an airbag message. Also my AC is not working

You have already discovered the root of problem ! .. Question is exactly how much damage the rodents have done.. I guess they'd eat the whole damn truck if they gnaw steel.. It's just going have to be inspected to find out what damage has been done .. I will bet that there is nest inside the heater/ac blower that's causing the noise when fan is turned on.. All ANYONE can do here is wish you good luck with it .. BTW ... Do you like cats?

like i said before,my big fat cat don't go outside no mo,BUT my neighbors cat is like the rat patrol. i just went out to my truck(2:30 am)she was out there, just on her rounds.ain't seen not nary one rat.