got a few question for headunit install for one of our cars. its a is300

1. is the labor same price whether i purchase a headunit there or i bring my own? can i a quote please for the labor and parts, not include the headunit it self. is there anything else need to be done beside the headunit instllation?

2. will a headunit alone be sufficient for the stock speakers, or need an amp etc? im good with the quality of oem audio, dont need full audio like others.

3. familiar with grom? can that be used for aux 3.5mm headset jack on mp3 player/ipod/phone etc.

thx fellas.