OK for the tv to work youll need a new tv tuner, whats available now im not sure that Asuka dont sell them (so i read)
getting the tv working while youre driving is not advisable and against the law, but if you HAVE to, there are override boxes that can do all this and literally just plug in. they come from japan, im surprised your car didnt have one fitted already!
check under the DVD tray andsee if there is a green light that is also a button. thats the override button for the tv.