Can you plug anything into the 2 in 1 adapter without hurting the Treo 650…cassette adapter, FM transmitter, “big” headphones????

I want to be able to listen to MP3 over the car radio and then talk (having the other party’s voice come over the radio speakers) when a call comes in.

Right now, even with the Treo hybrid headset, the speakerphone fights to come on making clicking sounds during the conversation.

This is only ONE OF MANY PROBLEMS with this Treo! Very, very disappointed and frustrated with this device and the lack of support!