Karma is a very sophisticated concept in Buddhism and is not as
simple as the term Cause and Effect. But in general, it means the
result of action. You can't change the effect, but you are able to
dilute the effect, but doing repentance regularly and
wholeheartedly.
You could reborn get out of the six realms of rebirth, but it
will not be easy because only Buddha will be totally out of this
cycle of rebirth. But by personal cultivation, like meditation,
chanting, reading up sutras, you will reborned into the 3 good
realms (Ashura, God and Human). Of course, this is theory in
simplicity because it depends on your karma too. Upholding 5
precepts is only the basic, which will keep you out of trouble, but
if you read up on this 5 precepts, you'll find that its alot more
complicated that you thought because certain things you thought you
could do, but it'll gain bad karma. Going vegetarian is good, but
if you find it difficult, you could do it slowly, like having one
vegetarian meal a day. Vegetarianism will not only improve your
health, it will also cultivate the compassion within you.
Hope this clears some of your doubts.
