There is a few ways you can go... Using the bottom connector of the iPod gives better sound quality. Using the headphone out socket on the iPod gives lower sound quality.
- Pioneer iPod adapter which plugs into the IP-BUS socket and into the bottom of the iPod. It charges it and gives good SQ. But locks the iPod so you have to control it from the head unit.
- Use a lead from the headphone output of the iPod to the AUX input of the head unit. No charging, lower SQ, control from iPod, cheap.
- Buy a cheaper adapter which uses the bottom connector, charges, good SQ and possibly control via iPod.
The last option is probably the best but i've never done it and wouldn't know what brand adapters offer this. Someone else will have to give recommendations on brands.
I've modified Pioneer adapters to allow control from the iPod but it causes a few side effects like not turning the adapter off when you turn the car off. You need to unplug the iPod before leaving the car. So it's probably best to buy one that does what you want to start with