The values of the resistors (and caps) are right there in the firstsecond page (well, the first one has the NMS8245 circuit ... the values should be same). Google translate is your friend with these kind of documents. It wont be perfect but usually close enough there should be no ambiguity. I think this mod has been discussed on this forum, you might want to use the search. I have not seen English documentation anywhere (actually even this Spanish one is a bit difficult to find; it's linked in many places but the links are pointing to a wrong place). I do believe an English translation would be welcome! 
However, when doing any H/W mod you should understand what you are doing (maybe not 100% but at least somewhat), not just follow blindly instructions. There can be errors in the instructions - something an electrician will notice since they are trivial for someone who is educated, but someone who has no idea, are not. It is also a lot more easy to make errors if you don't understand the modification. I've learnt this by practice. 
I'd look for someone more able near you to make the modification for you or at least help you. If you want to attempt this yourself, and there's still something unclear after using search and Google translate, just ask here. There's a lot of Spanish-speakers here (not me, though) and probably also many who have made this modification. By a quick glance making the mod should be quite straightforward (I didn't go through it thoroughly, though, or use some translator)... looks like the rest (after the schematics on the first page) are just examples how to do this on the NMS8255/50 MB. Yours is 8280 so of course you need to adapt them (assuming the MB is not similar).
EDIT: I actually just skimmed trough it with Google translate. The modification is not identical to the NMS8245 circuit, but mimics it. They've (at Aquijacks) made it more simple so it is easier to make. Google translate does quite a good job with translating from Spanish -> English IMO 
