I would look at the GTX 560 Ti over the 560, you will notice a heck of a performance bump with either but as the 600 series is now out you should be able to find a 560 Ti under 200 dollars if its on sale or rebate
I would go ahead and remove the cover then strap the fan onto the end of the cooler where the stock fan used to be at an angle. Tape up the rest to where all the air from the fan is going through the cooler.
Better still, remove the dead fan compleately, or at least cut its blades off so the new fan will work more efficiently. That way the existing cover can still direct heat out of the system and the heatsink will work as intended.
Where would us cheapskate modders be without cable ties and sticky tape?
Thanks for the replies, I would like the 560 Ti ,but not sure if I can spend the money right now.
I put a second fan on the 260, but as nforce and coozie said I may need to adjust the directions the fans are facing for them to work better.
If you do decide to go the 560 Ti route i would recommend waiting a little longer as the rumor mill is churning there will possibly be a 660 Ti released soon which I imagine will drop their pricing even further as distributors try to sell off excess stock.