I keep looking at these ipod adpaters online & I see you can plug them into where the factory cd changer din cable plugs into. The 2 factory decks I have don't say on the cd changer controls or anything like that on the front but I have the din cable plug in the back of the decks, does that mean I can buy 1 one of these adapters for my deck & it work like it supposed to????

If the din plug is for a changer, then yes.

The only Honda OEM HUs, [factory decks] that had a din plug that was not for a CD changer were older ones, the din plug was for an off-board EQ and would have a "dummy plug", [jumper] plugged into it if no EQ was used. 94