Always make components of objects such as doors and windows, this way if you change one the others automatically update.

Make sure when using Sketchup the white face of the object points in the direction the face should be seen, if the blue face is visible select the face and right click the mouse and choose reverse faces from the option list.

While drawing a spline make sure weld vertices automatically is checked on, also instead of using the pan tool "middle mouse button" press "i" on the keypad. You will find that the viewport moves to the position of the mouse cursor.