There are a few ways of doing this. If you have a air compressor, like ramenth suggests, just buy one of these stripe removal tools with the eraser head. They go for about $50 bucks or so.
Otherwise you can do it the old fashioned way, with a heat gun. Just peel off a corner of the stripe, heat the stripe so it gets warm, (not hot) and peel away. But if your stripe is pretty cracked up like you say, it will take some time. Then get the glue off the car with some adhesive remover.
Here's a picture of the stripe removal tool