I wouldn't use WD-40 as it leaves a greasy residue that will prevent the new stickers from adhering.
If you don't have Isopropyl, you can use Goo Gone. It's pretty good, especially if you remove the residue with something else after it (it's a bit oily).
Lighter fluid also takes most glues off and leaves the surface ready.
And if it's a metal body camera, you can even use acetone (nail polish remover). This will remove everything off the surface and leave it ready for the new covers.
But if the camera is plastic, it will melt a hole in it!