Quoted from Skins:he leaves positive feedback.
I don't beleive there needs to be feedback. Definitely have to mark it as shipped, and then wait the requisite number of days for PayPal to clear the funds. The wait time varies by how its shipped and what ability eBay has to track the shipment. If the shipment is prepared thru eBay, then the funds are released earlier as there is a way for them to track delivery. Absent the eBay tracking ability I think they hold the funds for 21 days after its set as shipped.
That said, if the payment looks like its not right, don't let it go. Personally, I'd ask the buyer to undo the PayPal, and go cash for the machine and receipt on pickup.