Just the wheel? It's a generic part, so you can probably find local stock if you search for "3-pin B103 10k" wheel pots
Most of the parts listed in the various BOMs can be found elsewhere by searching the part numbers
Just making sure, you are running your wires according to the RGB lettering in the guide picture, not the colour of the traces right? The colours are for YPbPr component video config, which is not the same as the RGB VGA output
Scratching the solder mask off the vias is normal. Some Wiis have exposed vias, some are covered.
You can keep following the G-Boy manual, all the principle information is still correct for a G-Wii. Just correct for part placement and it'll be fine