This answer by gomad and the link to the wikipedia article it contains may be useful to you. While that question is about the diferences between Star Wars D20 and saga, the similarities between AD&D 3.5 and Star Wars D20 could make that a valid answer.
ok, I managed to find somebody with a rulebook from saga to borrow, so I'll try to adress your questions.
Force Points: Every character has a pool of force points with size equal to 5 plus has half his character level (rounded down), regardless of class. Certain feats and prestige classes increase the size of this pool. A level 1 character start with its pool full of points. When you gain a level, your pool refills, but if you have force points over your maximum, the excess points are lost. Force points can be used the following ways:
- You can spend a force point as a free action to gain 1D6 to a skill
check, ability check or attack roll. Going up in levels increase the
number of extra dice granted by force points(2D6 at 8, 3D6 at 15),
but you can keep only the one with the higher result when rolling
- You can spend a force point a swift action when receiving damage that
could kill you. You instead end with 0 hit points and unconscious.
- You can spend a force point a swift action to lower your dark side
score by 1 permanently.
- Also, you need force points to activate or enhance certain force powers, if
you are a force user.
Usually, you can only spend a force point per round.
Destiny Points: Destiny points is part of a optional system in the game. If the DM allows it, you may choose a destiny for your character (or the DM chooses one, and he does not have to tell you which one). This does not have to happen at level one. A destiny is a long term goal for your character, and it gives you temporal but substantial benefits when your actions follows the path marked by your destiny, temporal but substantial penalties when your actions oppose your destiny, and a permanent benefit when it is finally fulfilled. Those benefits and penalties are the only clue that a character to discover his destiny if the DM choose to keep it secret. Also, having a destiny grants you the ability to gain and spend destiny points. Destiny points are gained at a one per level gain (including level 1, if the character starts with a destiny). Destiny points can be spent to gain benefits like: turn attack checks into automatic critical attacks,turn received attacks into missed attacks,change your initiative, shielding others from damage, partly refilling your force pool and empowering certain force powers.
Skill now are either trained or untrained. At first level You select any number of skills from you class list equal to your intelligence modifier plus class modifier, which become trained. Later in their career, the character must take the feat Skill training to be able to select a skill from his class list(or lists, if he has more than one class ) and make it a trained skill.
Note that a skill check is D20 + ability score modifier + training bonus if applicable (+5) + half your character level. So apart from taking the feat to gain new trained skills, you improve all your skills just by levelling.