I would like to bring some balance to myself: in reality, one or two little scratches on a front element, or a bit of dust in the lens won’t actually hurt your image quality ‘that’ much. Living proof:
LensRentals USA found a spider (yes a spider, you read that right) in a lens. Their observation: “We did, of course, take some pictures with the lens, including some f/22 sky shots just to see if there was any way we could see it in an image, but of course we couldn’t. The pictures were perfectly normal.” http://www.lensrentals.com/blog/2014/09/the-itsy-bitsy-spider
And regarding a scratched or cracked (or more like smashed) front lens element, this is a rather extreme case, even this lens could take some (reletavely) ok pictures given the right conditions: http://www.lensrentals.com/blog/2008/10/front-element-scratches
