There is no restriction for basic mov't like 7S26, 6R15, etc you can get all parts. Going up to middle-level you can send a request and they may try to get it. No parts for Grand Seiko, which can only be serviced in Japan.
Not really. There is no material house that sells online in Japan, and even if there was they would probably not ship overseas. You can, however browe on Yahoo! Yapan and buy there using an agent.
Fault at third wheel. ( minute)
Clean and inspect all ( gear teeth and pinion) of the minute wheel under high magnification. There is a slight possibility of bent pivot or damaged pivot hole, enlarged pivot hole cause depthing and exacerbate the condition.
I should have mentioned that to become a "authorised service centre" companies had to install the recommended Swiss tools even if the tools already being used were perfectly good they had to be replaced. If my memory serves me well it was in the region of €50,000. Many experienced horologists just retired and who could blame them.