Well shit, she has a really good point. A practice student so he can learn how to teach, that's a great idea. Granted, showing her how to operate the machine will be significantly easier than trying to show her how to fix it, but this is still a pretty good starting point.

"Okay, well. I've always thought that the best way to learn something it to just dive in, soooo. Here we go?"

So, he starts pointing out different parts and explaining their functions, showing her the sort of damage to the parts that he's looking for, how to remove and reattach them. Things like that. It's probably not the most exciting lesson ever, but Peter is very much in the zone, nerding out about technology and how it works.