Opossums are pretty much all show and not much substance. They hiss and drool and if that doesn't make you go away, they will keel over and play dead.
Here is an article from the LA Times you may find interesting.
http://www.latimes.com/style/l...
We have one that got so comfortable here, that in the evening when we gave the cats their supper, she would sit the edge of the breezeway with the cats. We discovered that she was sleeping in the greenhouse in an empty pot....along with one of our cats.
Do be careful about taking the opossum away, it could be a female with babies nearby. We talked to my SIL about the dangers. She has a veterinary hospital in the Sacramento area. She assured us that Opossums are not a great threat to people or animals, because firstly, they adhere to the flight rather than fight and if all else fails, they play dead.