I found TV was a bit of a waste. if I had to go back all over again, I would probably just fit FM band expander on radio and wire the Garmin on the Japanese TV's Aux input. That is probably the only 2 things that I would use pretty much on almost daily basis. Saved me a few hundreds, but since I got it now, I will keep it.
There is a DIY thread on M35 Stagea section showing how to wire Aus TV tuner e.g. Asuka or HiTV unit into the japanese TV tuner's Aux in.
Do a search there. I don't have a direct link, sorry. The basic wiring principle would be similar to V35.
FM band expander any car audio shop can do if you don't want DIY. Otherwise there's lots of ppl who has done it themselves, ask around this forum.
I was told it was just inline connection in the aerial plus finding a +12V and ground. Doesn't need rocket science for that.