Shipping is the one thing you want to investigate if you decide to buy a whole fender or anything thats shipped oversize.
When I bought my quarter panel, I had the shipping fee waived. How I did this was I had my order piggy backed in with a larger order by another party. The vendor was getting an 18 wheeler load all at once. How I understand it is that large orders PO'd get a shipment cost reduction.
I see part prices all over the place from decent to outrageous. So it pays to get some quotes. Make sure to ask, in stock, insurance cost and whats covered, shipping time, where its actually being shipped from, do they have another location they ship from, tax included or not, carrier name, actual product mgf'r, can you decide on what carrier to ship it.
Also its quite often cheaper if you have the item shipped to a business instead of residential.
If you can work with the seller on shipping, this is a good website to get ideas on what it costs to ship.
http://www.uship.com/price_estimator.aspx