Stupid audio question.

The stereo in my 2003 Envoy has a button that says CD/Aux. It's the one I use when I switch from radio to CD. Does the "AUX" label mean that there's an aux input jack on the back (there's not one on the front)?

I want to use an mp3 player in the vehicle. I'll probably end up with an FM transmitter, but I thought I'd try this, first.

I want to say the the cd/aux button switches from radio to cd and if you have a cd changer will switch to the changer. I haven't seen any envoys with aux jacks for plugging extras into. Go with the fm.