I want to redo rotted trim around a window on the outside of my house. I am thinking to use pressure treated because it is in a location that gets a lot of shade and retains moisture, probably accounting for the rot on the side of the window.....soft wood, a window which has been in that location for 30 years. But the left side trim board is what needs replacing. I can easily cut the board for general thickness. The original has some steps in it. Should I use my circular saw with an additional blade on it and line that up, or a router set up?