I want to upgrade my radio and was wondering what i need to do to change the head unit and bypass the factory amp.

 

You need to purchase a CAN-BUS. So go into a car audio shop and let them know you need a CAN-BUS for a 2008 Dodge Ram. I believe that that is all you need for that and it will bypass the amp. If not, take out the wires from the amp and connect them directly to the speaker wires leaving the amp. You've got a lot of wire testing to do to make this happen.