Oh, regarding the 3% fee that so many tack on for using PayPal -- I believe it's explicitly prohibited by the rules of PayPal. That's why you never, ever see people charging the 3% on eBay, because eBay enforces that rule.
Personally, I think it's a bunch of crap to dump that cost to the buyer. Nowhere else that I can think of does the buyer explicitly pay the fees for credit card processing. When I go to Home Depot, the price is the same for cash or charge. Now, that cost to Home Depot is built into the cost of the item that I'm buying, so I end up paying it for (or at least sharing it with) Home Depot. So, regardless of the rules of PP, I think that that the seller should pick that fee up, as it's so traditonal in selling. Also, the buyer is paying shipping and sometimes handling.
So, as far as ethical and legal -- don't charge PayPal fees to the buyer.