Just some thoughts..
The shipping rates were weird.. $10 for shipping and $5 for insurance? If anything, pad the shipping, but not the insurance. You are just encouraging them not to get insurance, even if they want it. $10 for shipping was inline, but $5 insurance was not. I would've personally charged $6-$8 for shipping and add $2.00 or so for insurance.
I don't think it's necessary to post the reserve price. That's just me though.. I usually don't like to give warrantee's either, but in the case of your modded card, it's almost mandatory. The potential buyer has no idea what you did with this card.
This also leads to your feedback rating. You don't have that many feedbacks and this isn't a great item to sell for a newbie. There is too much trust involved IMO and your feedback rating hasn't really established you as a completely trustworthy person yet.
You probably should have said that the stock fan was too noisy instead of that it cooled better. This implies OC'ing.. Especially to me it does.
There are other little things that have been covered here.
I think that my biggest problem with your auction would have to be that you modded the card. Most people that buy on Ebay probably don't know about what you did and why you did it. I think that might keep them away from your card. Also, the fact that you modified it, implies overclocking.
This is totally different, but the same as far as I'm concerned. When I look to buy used motorcycles, I always steer clear of modified bikes. You never know if the mods were done correctly and people that mod their bikes, usually abuse them, so I always go for something that is bone stock.
I'm just babbling now.

Good luck with your auction.
Sal