The cartridge is what gets lubricated by the oil, so if the turbo is leaking that's what you need to replace. It should also come already balanced.I'm over on the western coast of Canada. And regarding the turbo, i have absolutely no experience regarding it's internals, but could probably figure it out. I've linked what i presume you are referencing at the bottom here. Are the seals in the cartridge what would be leaking? I'm somewhat mechanically experienced, but I've heard that rebuilding turbos yourself is tricky.