I think it's "logomorph". But, yeah. Perhaps his statement would have been better with "A mammal's a mammal"...Though ome people don't classify marsupials as mammals for one reason or another, which is silly as they have mammary glands- the only defining characteristic of a mammal.
I'd imagine that the problem with breeding opossums would be legal and practical more than any safety issues. I'm not sure about the laws in TN, but here in WV you can get into deep doodoo for capturing and keeping native wildlife.
Also, how do you plan on capturing them and mating them? I suppose a live cage trap would work, but the bait you would use may just as likely get you a raccoon or a skunk. And as for breeding the only opossums I've ever seen up close have been dead and I;ve usually been focusing on their impressive teeth, so I don't have any idea how to sex them.
I would look up your state's Department of Natural Resources and look into the laws concerning native wildlife first. The rest might just fall into place afterwards.