Upload & Sell: Off
if it looks too good to be true... it probably is.
None of us here has any inside track on whether the seller is actually legit --- but if they are, they must also be dangerously incompetent (otherwise, why not wait a few weeks until the product is ready to ship, then sell for hundreds more?).
In past scams that this might mimic, the seller will use the money from later sales to actually buy/ship computers to a few earlier customers (hence the shipping delay), so that they can maintain the appearance of legitimacy long enough to disappear the rest of the cash into untraceable forms (and maybe score a few more sales off the positive feedback) before PayPal comes chasing after them.