Taking out the OEM radio was easy, but how about an Alpine head unit?. I don't see the holes like on the OEM radio that the removal tool fits into. I think the DIN plate with the tabs bent would make it hard to remove the head unit.

 

It depends on the age of the Alpine deck. On newer decks, there are a set of keys required to slide alongside the chassis of the deck, on older models you can snap off the trim ring around the face plate and you will see a small cam lock on either side of the face plate that locks the chassis into the cage.

You can try finding your specific model at Alpine Website and go to the tech support page; you can log in without registration and get pdf files of owner's manuals there.