La2venida

Want to install after market stereo into Audi A4, Quattro,(concert system with bose speakers). what websites do you recommend to find the connector harnesses i need for the stereo, and do i need anyother (i guess i need antenna connector), but website makes it easy to figure this out. I have found websites and the harnesses i need, but not fully sure if its for my systme. and what do i need to know and do for disconnecting batttery (first time installing stereo, and disconnecting the battery on my audi.).