Yeah, but with Apple they can get help from the genius desk at the Apple store.

For both windows and Linux you'll have to find someone thats willing to help you, essentially. Usually a lot harder for those people. Especially with Linux ime, as even fewer places know enough to help you, even if they may be able to handle windows

I believe there is a whole market dedicated to give assistance to windows.

To use Linux on the desktop you first have to know about it for a start, so you are unlikely to end up with a linux OS without knowing anyone using it or an association/usergroup promoting it.

For both you can just call your local PC shop, which are much more common than Apple stores, at least around here.

In vast parts of America, the "local PC shop" doesn't exist. It's BestBuy's GeekSquad (of dubious quality) or Apple's Genius Bar. There might be a repair shop somewhere, but most of the time, they just repair cracked screens.