If I Buy The Iphone G3 Can I Download Songs Illegally And Transfer Them To My Iphone 3g

I use Limewire, and I download songs illegally. I was wondering if I could transfer my illegally downloaded songs to my iPhone 3G. If so, do I have to buy an accessory to do this? Or can I just plug it up to my computer and transfer the songs to my iPhone 3G?