Everthing in a manual can be reversed for a southpaw. The difference is that most of your opponents will be fighting out of the othodox position which means your going to have to become aware of your foot position inrelation to theirs. Find out the advantage of having your front foot inside (to the right) of theirs, and also find out the benifits of having it on the outside. There's an artical on the sub-board by greynotsoold that you can reverse to meet your own ends.

You still gotta work on everything else and you to develop some good quick counters to the body. A cross, and hook to the body, or a jab + a short left to the solar plexus are a couple good counters that you should become familiar with. Keep in mind your foot position because that will effect your ability to cut off your opponent and land different shots. A good right hook is an important punch in your arsenal and you should learn how you can counter with it.