The Original trilogy stays the same.
The events of the prequel trilogy need not change and in fact the prequels as they exist now need not change in any way to exist happily with these revised prequels. However, the focus of the stories should be on a new group of characters, with Anakin and Obi-wan featuring in the story only briefly. The theme of the prequels is primarily one of establishing the universe of Star Wars, thus it remains quite basic. There is a war between clones and droids, yet this is merely a backdrop for a smaller struggle for survival going on throughout this tumultuous time. The story follows a crew of space pirates, reduced to scavenging the battlefields of the galactic war. One of these is a young girl who rescues Anakin who has frozen himself in carbonite to prevent a battle injury from claiming his life. Through this encounter, he instructs her in how to be a pilot, a primary theme of the trilogy. Later on, she starts to come to terms with the idea that she may in fact have some power in the force, and her psychic connection with Anakin drives much of her decision making in the films. Having rescued Anakin and rejoined her companions in Episode 1, she joins the Republic in Episode 2, flying a stunt fighter under the command of another Jedi. Then the clones turn on them with the issue of order 66, and she flees into hiding with this Jedi. Episode 3 takes place in the aftermath of the Jedi Purge, where she tests her mettle against the murderer of Anakin, Darth Vader, and there is one final stand to protect the secret location of the child of Anakin (In these, Vader is not revealed to be Anakin, the existence of Luke's twin sister is yet unknown, and Yoda is hardly if ever mentioned).
In the sequel trilogy, it is revealed that the emperor in Return of the Jedi was just a clone, drawing the Rebellion into an inescapable trap where they were almost completely wiped out after the battle of Endor. The true emperor remains at large, and Han Solo, Lando Calrissian, Chewbacca, and C-3PO are all dead or destroyed on Endor. Luke, Leia, and R2 flee the carnage in the Imperial shuttle, and Luke tries to train Leia in the ways of the Force.
The sequel trilogy opens with a new crew of characters, one of them being the son of Han and Leia. There are numerous revelations about the Force in this trilogy. One is that Luke and Leia are not brother and sister. Obi-wan had no knowledge of the 'other' that Yoda referred to, and so he could only trust Luke's intuition in that situation, which was wrong. Another revelation is that anyone can train in the ways of the Jedi, and the dogma that the Force runs in families is a lie perpetuated by the Jedi to keep their power consolidated within a small in-group. However, ability in the Force is fostered much more easily when a Jedi can use their powers of suggestion to make the trainee believe that they have ability, and they even use their powers to accomplish feats for the trainee. This is a closely guarded Jedi secret, one that is lost to Luke until it is too late. For he cannot train Leia to be a Jedi, as her mind is too strong to be manipulated. Here then is the great weakness of some Jedi trained later in life: they are essentially weak-minded. This is why children are taken by the Jedi at such a young age, when their mental powers are still forming, and why Luke was able to be trained even when an adult. With these revelations, Han's son embarks on his own quest to understand the Force, and these revelations will lead to a new clone war with the Force itself used as a weapon of mass destruction.
