Take a camera. Make a mini-vlog - packaging the iPhone, weighing it, shipping it with the tracking number. If a chargeback does happen you'll have the shipping proof and the whole video (the weight proof will definitely make you win if he claims empty box).
damn. 3k lol. i would do it personally. you could win that paypal dispute. although i have only lost one paypal dispute, you could win that. just provide the tracking number and upload a fax or whatever they want you to do and you should be fine.