Ok. So I got the radio out. And all the connections look connected fully, but I'm not getting any sound. Possibly the amp? Any ways I can check?

yeah use a multi meter on the 12 V constant to the amp and ground it out . then turn the vehicle on and the radio if the amp is receiving power. if the multimeter indicates that there is close to 12 V being recieved then it may just be an inline fuse. if not then check the connections to the radio. is it after market or oem? or if that is not hte case then check the rear speaker harnesses (easier to check than the front) and make sure the speakers are connected.