heh, getting the resistor out is not a problem, problem is finding which resistor to take out.
If you can find the right one according to the info you find online, then you have to use soldering iron, heat the solder joint, take a desolder sucker thingy(can buy from diy shop, home fix etc) suckkkkkkkk up the melted lead, remove the component, put in new one, solder it back.
Heh, if the above is too difficult, i suggest some methods.
1) Change placement of wah in the effect chain and try again
2) Find someone who can play or at least listen, listen to the problem you find in the setup and decide if its really valid
3) Determine if the problem of weak sounding wah, is it an inherent design of the wah pedal itself or placement problem, wah-ing technique problem or some other reason, before jumping straight to modding.
oh lastly, if still wanna spend more money, then get a new wah. Spend less money, find out the mod thats available(more than enough sure to find after googling it) and diy. Dont want to spend money, relearn how to use the pedal with different placement in signal chain and gain adjusment/control