I have a PAL n64 console , with a video encoder chip that cannot be rgb-modded. I also have from eBay (bought it ~1 year ago) a VDC-NUS A BU9801F chip , that can be modded for rgb AFAIK. Can I replace the chip on my mobo with the NUS A one and make a succesfull rgb mod?
you can, i did it. it is pretty easy to switch out the chips so you won't "butcher" the n64. all you have to do is get a soldering iron and heat up each of the pins and pry that pin up lightly with a pin, holding it for 3 secs so the pin doesn't reconnect. do that to all of them and lift the chip away. to put on the new chip just put it down and line it up as best as you can them touch the pin with the soldering iron point and it will connect really easy.
i have done this with both the pif and dac on my n64 and it is still good