The hardest part is the miter cuts. Unless you got a nice Craftsman compound miter saw like I have, I would go for those attractive corner pieces that join two pieces of molding together. They are easy to use and look great! If you have corners that are not square - like most of us do- you will need some good wood filler to hide the gaps. If you are painting your trim, not a problem. If you are staining, better wait for the pro to answer your post!