[mothered]

Should I get it from apple, Amazon, or somewhere else?

Although Apple tend to make a one time exception with refunds/replacements, the value of your Item Is too high.

Amazon has been hit left, right, and center hence Is the better choice.

I'm thinking of using a sealed box method. I'm thinking of picking up an old broken Mac mini to replace the one inside. They are the same dimensions and weight. Will it will work?

Only the weight counts.

As long as It fits In the box, the dimensions are Irrelevant.

From watching videos online, it looks like they only use a plastic wrap, so I'm wondering if anyone knows which type of film they use?

Checkout this to see If there's a similar film.