The only two questions you need to ask:
How much is it?
When can I take it?
If you're buying a pin from someone's basement, they likely don't know much about it. To them, it's just an appliance that's taking up space. It's up to you to determine what you want to know about it.
Most of the questions that you listed are maintenance questions that you can find out by either reading through the manual or with research on the internet.
But, some folks are happy to chat about it even if they don't know much about it. It all depends on the person and their situation. If the seller is inclined to chat, I try to get a bit of history on the machine--how long they had it, where they got it, etc.
If you're buying from a collector or retailer, that's a whole other story, and they are typically more open to questions and discussing the care & feeding of a machine.