Re: sticky material left by decals
Use 3M wax and adhesive remover. Fromulated not to hurt the paint and if you let it sit on the adhesive, will take it right off. I debadged the entire back of the car and this stuff works awesome.
Available at any auto parts store and maybe even big-box store like target or walmart.
As the above poster said, make sure to apply wax to the area when you are through...