Answer A.) First, fully clean the seals with a scrubby. Then, cut the films dead on the outside for a clean install.
Answer B.) You can remove the seals by pushing them out and then rope them back in when you’re finished. Just be sure to loosen or remove the interior panels first.
Answer C.) Make your pattern 1/16th of an inch short on the top and one side. This will create a perfect fit, as you’re making up for your blade flexing the gasket.