Does Anyone Know How Effective the Exelo CO2 Laser is for Acne Scars and Stretch Marks?

My PS included me in a clinical trial for the removal of stretch marks using the Exelo CO2 laser. I would like to have some minor acne pitting on my cheeks removed as well, but am unsure if it would be worth it with the same device. His office offers several different modalities and I would like to know the best for my skin type. My coloring is light to fair. If anyone is aware of the cost of a partial face treatment I would appreciate that info. too! Thanks!