Do i have to buy a harness for my D3? Or is that optional. Can I still do the bypass? Or do I have to get the harness. Please someone help. Any other info. will help. please lend me all the knowledge you have. Thanks

The avic will come with all the harnesses neeeded to plug into it. You will need a harness for the vehicle you're installing it into.

oh i see. tahnks. and can i purchase the harness for my car at my honda dealership. Oh can i find it at like bestbuy?

You're not going to find it at the dealer. Any car audio shop will have the harness you'll need.