Any info on replacing HSF on my video card?

[Darn]

I have a Gainward GF3 MX400 twinview. The factory fan is shot making a bunch of noise and vibration. The fan sits down inside of the heatsink so just replacing the fan is probably not possible. I would rather upgrade to a larger HSF anyway to get better cooling but I am not sure how to get the old one off or what is the best method to attach the new one. What is better thermal tape or epoxy? Where is a good place to purchase the product you recommend?

Thanks in advance for any info you can give me on this subject.