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Nikhil,
it is not at all difficult if the spirit is willing.
You would require a good soldering skills and infinite patience (very imp. !!!)
anyways , considering the cost of your card and the immense risk that you may be contemplating , i would suggest first you try to get hold of a cheap , disposable tnt2 or GF2/4 mx series card. (costing from rs. 250 to about 800 Rupees). work on that. gain some expirience , meaning break / damage those cards first.
(you would be amazed how much you can learn from ur mistakes while hardware tweaking .....)
once you are fairly confident. try the pencil mods first. these are relatively very "easy" and can be removed too incase you have to RMA the card in the extreme case that you may have to opt for warranty issues.
once you decide about volt modding kindly post about it here on the site under a different heading. i and many of our co-members will help you to achieve that with as little "pain" as possible.
but i once again remind you that these tweaks / mods etc "can" permanently damage ur card. if that happens kindly do not blame it on others.
ps: I will be volt modding my X800XL card next month......, will update you guys of its status as and when it happens.
"The spirit is willing but the flesh is weak" is my current condition........