It looks like you can get a camera into that space below and in back of the oven. I would glue and staple the plywood back into place. I'd then go into the compartment from the outside (where the cord is stored) and glue/attach either a small ledger of wood or an aluminum angle piece so that the rolled cord doesn't do the same thing again.
I don't know about the oven, having an opening that big wouldn't be my choice but I have no idea about the design. I'm thinking there should be an attached piece of metal in there to seal it up but...? The temperature in that area will probably be lower than the oven compartment because it is below but how much...?
Good to hear you have a plan of attack regarding these repairs. Yeah, you shouldn't have to do them but that is the way of TT's, they are not built with exacting standards in mind. Also, a slightly deteriorated shock absorber wiper is to be expected. It is rubber, after all. Don't spray any WD-40 close to them, that is just simply bad advice. WD-40 does react with certain rubbers and may lead to a full dissolving. Use silicone if you must but it's basically unnecessary.
I would expect the dealer to be somewhat confrontational with a customer that brings in a list of 20 items. That is out of the norm.
