Lessons are very important to learn correctly. Sure you can learn how to post yourself. Whether you learn to do it correctly is a different question. Personally I'd invest into at least 2-3 months of weekly lessons (wont' hurt anyway ).
As for the saddle if you don't plan on any jumping I'd look into dressage saddle: the legs are more straight (kinda similar to the western saddle), and it's usually more deep and comfortable than CC (purely my opinion, other people may not agree of course). You can also look into A/P, which is usually deeper and not as forwards as CC (although I had rather bad experience with A/P saddles: I don't fit in most ).