It's the way aluminum behaves when bent or strained that causes the stain-like look. Unless you can muster the force with pliers (which is very difficult), your best option is to replace the [product|IF188-096], [product|IF188-087] and [guide|38545]. Keep in mind that this is a very difficult repair, and does require time and patience. Additionally, you will need several specialized bits, including a P5 Pentalobe bit, and T5 and T8 Torx bits.