No, the XJ Cherokee does not have the same heater box as a WJ Grand Cherokee.
Condensation is a normal byproduct of the compustion process. Unless you have a gallon of water coming out you do not have a problem.
You will have no problem with that switch over.
I had the same problem with my 1997 Grand Cherokee and it was the dash mounted automatic light switch. The problem was also solved by turning the headlamps on manually.
I had the same problem. Google "keyless entry remote 2003 Jeep Grand Cherokee".
Whats the problem? cant help you unless you describe what its doing/not doing.
Yes they should interchange without a problem.
no, the Cherokee and grand Cherokee are different vehicles
Low coolant or bad sensor
The most likely problem is the blower motor making the noise. It may be necessary to remove the box to find the noise for sure.