JSW:
You don't HAVE to do any maintenance that you don't want to do. That being said, we all know that regular maintenance is the best way to insure that our Durangos are in top shape, and will be dependable.
At 105K, the plugs are up for replaement but they can go another 10-20K if needed. Your coolant SHOULD be the long life purple type which is good for 10 years or 150K miles. That was not needed yet.
The trans, diffs, and transfer case would also be on my list at 100K, but you can do them piecemeal unless there is a specific issue that might be related to one of them.
The AC condenser on the Gen 3's is not uncommon it seems, as is the trans cooler. $1K is the going rate at the dealer. More than 1 D owner had reported that their dealer performed one or the other as a "goodwill" repair for a$100 deductible. I would not be happy that your dealer had you change the coolant 50,000 miles before it was due. Unless the plugs have already been done, they should have been done instead of the coolant.
Don