Hi!

If you've got the pinouts and you're **sure** they are correct, I
don't see much opportunity for any damage as long as you make sure
your wiring is correct.

Speaker and microphone connections on the phone and the car kit are
unlikely to cause damage to anything if you don't get them quite
right. However, anything to do with powering the phone or charging it
can ruin your day if it's not compatible (have you checked the voltage
and polarity?) or not the appropriate voltage/current output.

William