It's nice to see TL owners on this forum. I'm currently researching a Car PC, but every time I see a TL in the forum it makes me want to step up the process. Can you show pictures of the HU in the glove box? How was it mounted in there? Did you remove the factory speakers? I had read somewhere that the factory speakers were 1 ohm and not compatible with aftermarket HU.
The transmission of 2nd gen TL do have a high failure rate. They make no secret about that. The support for Acura is second to none. Mine went out and the replaced it free of charge, including the rental. I'm not even the original owner--I bought mine at the auction. I guess there was a class action lawsuit that extended the warranty to 7 years and 70k miles. Don't hesitate buying a 2nd gen TL!!!!