Skylights bring light, stars and the outdoors in to other parts of your room. Constructing a skylight with a flared, rather than straight, shaft will gain much more light with a simple expansion. Consult a professional structural engineer before tearing into your trusses, however!
These photos are typical of load bearing walls you will find in your home. Study these details to learn how loads are distributed and carried in a load bearing wall.
You can remove a low ceiling and move the structural ties to different locations for support. Consult a structural engineer before proceeding, and gain space for ceiling fans and a vaulted ceiling atmosphere.
Building a vaulted ceiling can be accomplished by the DIY'r, however you must be a very good DIY'r. Check first with a structural engineer. You don't want your roof to collapse. Try to think of building for the future with added electrical wiring.