Tom Wallis

To add oil you would pull out the blue plug and squirt some in the hole. The one in the picture is fine though. The oil should come up to just below the hole. Any suitable gear lube should be fine. You really don't need to worry about changing it for a long time.

Henderson's Line Up is great and I have been to them. But if I'm not mistaken they primarily do suspension, alignment and brake work and they are very good at it and come highly recommended. I'm not sure how much they do beyond that.
https://www.hendersonslineup.com/

When I first got my rig it had the roof bubble with the obsolete sat dish inside and all that wiring that you're referring to. I removed the dish and all of the wiring which went through a hole in the roof right on the seam underneath the dish. I then sealed the hole and because it's on the seam you can't even tell where it was. If your dish was already removed, you may have a similar situation.

I would say that a poor connection in the wire nut caused the wires to overheat due to high resistance. And 12 ohms sounds just about right for the element. After replacing any faulty or damaged wire and connections and testing as you suggested I would not be afraid to use it.

Well Bob, you're a pretty good salesman. I just ordered one from Amazon.com for $175. If it works half as good as you say it will be worth the money. It gets 4.5 stars from over 16,000 reviews so it must be pretty good.