Not to dissuade you from upgrading at all, but it should be very easy to find a replacement element. I just replaced one in a 30 year old oven for about $22 on Amazon. The tech really hasn’t changed much, just need the right shape.
If you decide to upgrade, look for a convection oven, but make sure it’s fully configurable. With countertoo versions, some never turn off the fan completely. I could see similar stupid design happening in full size units.
This kind of falls in the “if you have to ask” territory.
While it’s technically pretty simple (you’re just moving it, not setting it up initially), code has specific rules, and this is the knowledge you’re paying for with an electrician. Since code can vary, knowing the code for your area may be important.
May be worth a call to the electrician about the code and homeowners doing such work. He may not mind talking about it. Just be honest with him. Edit: ask your BIL about it, specifically the code side.
Check out Emily Cherkin, I heard an interview with her the other day (she has a new book out: A Judgement Free Guide To Becoming A Tech-Intentional Family), and what she had to say mirrored a lot of the comments here - communication with kids, working with them so they learn how to manage tech themselves (and develop a healthy relationship with it), etc. I haven’t read it, but maybe she has some structural ideas in it (she was a school teacher).
I can say first hand that using blocks, parental controls, etc, are limited tools that should only be used as a small part of the bigger plan (I manage these things for my family and extended family). These tools show that they almost don’t matter - there are successful parents with/without them in my family (I think mostly because all the parents didn’t allow unsupervised tech time when kids were little, so were able to teach some fundamentals organically).
Good luck out there!