I simply can't imagine any steps that might be taken to avoid marring the LCD while removing a cracked screen. By the time enough of the cracked screen is removed to allow protecting the LCD, it's already too late. I can't imagine a method through which removing a cracked screen wouldn't eventually become a process of troweling a stubborn sludge of adhesive and glass shards away from at least part of the perimeter of the screen recess. However, barring slight unremovable marks on my LCD resulting from the issue, I'm satisfied so far with the robustness of the the screen replacement.
It might also be useful to mention that fresh adhesive and retrieval of the camera bracket and home button assembly aren't necessary if the replacement used is iFixit's iPad 3rd Gen Front Panel Assembly, which includes those.