Why did the chicken cross the road? To show the possum that it could be done.
Opossums do raid a chicken house once in a while, but most frequenlty they tip over garbage cans in the night; and occasionally one will den in a garage or attic. They may harm a lawn if it is harboring lots of grubs. They can rob fruit from your fruit trees. They will eat food set out for pets and eat seed underneath bird feeders.
They can carry deer ticks (Lyme disease) only if they are within a few miles of a local deer population; and can have rabies; so they are not really desireable in the suburban landscape at all.
They do some good things for the ecosystem. They eat lots of slugs and snails and many pest insects such as grasshoppers, crickets, and beetles.
“Playing possum” which can last for minutes or hours, is an involuntary physiological reaction and may be effective behavior in some situations. The eyes glaze over, tongue hangs out, respiration becomes shallow, anal glands emit a stink, defecation occurs.