Angie,
Read this. I googled getting rid of possums and found it:
Getting Rid of Possums
Post By ashlee (Guest Post) (01/07/2008)
I've done this many times nothing works except leaning a trash at a 35 to 40 degree angle on something with ripe fruit in it the possom will climb in for food but can not climb out thanxx this really works
ily