I don’t know about warranty but they have an extensive parts list. I just replaced the battery on a laptop I bought 5 years or so ago from them.

I don’t think Xerox invented the computer mouse. It was first drawn out by Douglass Engelbart and presented to the public in the 1968 presentation “Augmenting the Human Intellect” (you can watch it on the present day, it was recorded).

It was my understanding (which I did not verify) that this was picked up by Xerox and others and that windowing systems evolved from there on with Xerox leading towards Desktop Publishing.