HI I am new to this fourm. I just picked up a 2007 Mercury Mariner. The first upgrade i am looking to do is the Front door speakers. I purchased these http://www.crutchfield.com/p_1086829CF/ ... html?tp=92 i am wondering how easy it the removal of the door to get to the speaker is there any steps that could help me also i am wondering if there was a way to tell which wires are the + or - on the factory wires. Thank you.