I am looking into doing the same thing, from my research I found the following websites:
1. http://www.crutchfield.com/m_770/iPod-MP3-...ters.html?tp=15
2. http://www.soundgate.com/index.php?request...adfc55dfedf543a
You will not need to splice any wires with this product.
When I was heavy into car stereos I used sound gate equipment. they made an excellent product.
Hope this helps:)