Congratulations on finding another RV. I don't know anything about a transmission cooler but I have 2002 Coach House with the E450 engine. I bought it used in 2006 and have put almost 40,000 miles on it, The only problem I have had with the engine so far is that the cruise control quit working on my last trip. After a trip West in an underpowered Class C this one drives like a dream. Plenty of power to climb mountains.
Bedbugs, another good reason to have an RV. I usually travel alone and just don't feel safe in a motel. There are stories on the news of people being robbed or worse at just our local motels.