Don't worry about the 'E' already being there. Most of the modules have been mapped out already showing which each function means, just know that if it specifies E5 there, you need both values set to that for it to work. It doesn't necessarily mean one won't be the same as what is already there.
The '19+ do not allow you to set the top right gauge to the trans temp. They do have the Gauges function though that allow you to select Trans Temp as one of the options. They also have the Measurements screens which show all the live raw data.
As far as the Windshield wiper warning, that is because when you made the change in the IPC, Forscan reboots that module. Making most Forscan changes will bring up warnings the first time it boots up.
You can set Nav in Motion, which is just changing the country code to one that allows those functions. Be aware your speed limit signs will change to the Euro style look and the 911 assist will be disabled. Also it has been mentioned on other forums that newer versions of SYNC 3.4 allow changes in motion if a passenger is detected. It will prompt if you're a passenger. I have not tried this myself though.