The whole Time Lord thing was pretty confusing--usually I can keep up with the temporal stuff in Dr. Who, but I don't understand how they just now figured out they were going to be fucked in the time war, and then how they decided on that moment in time--when the Doctor and Master were on Earth--to make an appearance to do... not sure what, exactly. Smash Earth out of the sky so Gallifrey could take its place?
That moment for their return was dictated by the fact their very small and weak signal couldn't be located by the Master until he amplified his own senses to figure out what the drumming in his head was. He achieved that by creating 6 billion versions of himself, the joint effort of which allowed him to find the crystal that provided the link to the Time Lords. The crystal could only escape the time lock once he detected it as the source of the drumming noise. Once he had the crystal he could set up the contraption to link the two worlds.
The Time Lords were then coming the Lock, complete with their planet and pretty everything else sealed within the Lock (including the Daleks and various engagements and encounters that made up the Time War). Before all this could descend, the Time Lords were going to activate 'the ultimate sanction' - the end of time. This would wipe all time and existence leaving them to ascend to a different plane of existence for the rest of eternity, outside of time.
Yeah, very overblown. I had to watch it twice to get that, and even now I'm not totally certain.