Will I damage my vehicle, or surface by removing it using the methods you suggest?
Will I damage anything by removing the decal?
The vinyl decal will not permanently damage painted surfaces or glass windows.
The decal will actually protect the finish of your vehicle's paint or glass surface. However, if the stripe or decal is left on the vehicle for long periods of time (5 years outdoor exposure), the paint on the vehicle will fade slightly, while the paint under the decal will not. This will cause a slight shadow effect once the decal is removed.
You can avoid most fading by regular waxing maintenance. The fading of your paint over time has nothing to do with the decal itself. All vehicles will fade to some degree over time.