Is not "regular" AppleCare (not the "plus" version) still available IF you call Apple directly?
You should at least call them.
You bought this used, is that correct?
In that case, not sure if you can get regular AppleCare, either (may be available ONLY to the original owner).
Them's the breaks of buyin' used.
However, be aware that ALL 2017 MBP's are covered by a 4-year warranty for the keyboard, regardless of whether you bought used. If the keyboard fails, you get an entirely new "top case" (including new battery).
I believe the display is also covered by the "StainGate" warranty extension as well.
Since the display and the keyboard are the "biggest issues", I'd let AppleCare alone, and just go with the "factory-extended warranties".