Installing window trim (Interior Question)?

The ga .of nail will work fine the length should be 1 and a quarter for attaching it to the window at the reveal point and a 2 in. nail where you attach in the plywood. the kreg jig on trim?? not necessary. No miter joints??? but I would suggest renting a miter saw and having miter joints in the corners no other way to make a 45 like the one needed with out a miter saw.