They get there power from the allspark, it seems to be rigged up to supply power to the planet, I guess they must plug themselves into some kinda port for a recharge. When Megatron falls through the ice he states that his "energon levels are depleted including his backup supply", so I guess energon is the fuel sorce of the allspark. Megatron also claims to not know what ice is lol.
They fight because of the allspark, simple as that. Autobots protect it from Megatron because he want to exploit its power.
BB gets interrogated by Megs about the location of the allspark as he is trying to find it. However BB stalls for time so some of the other autobots can launch the allspark into space away from megs. They dont exchange infomation any other way other then verbally.
Shockwave isn't in it, niether is the Guardians. Arcee fights along side BB but she is killed by Megaron while he interrogates Bumblebee. Arcee is about the size of a human, she looks pathetic. Some of the Decepticons show similarities to other Decepts in G1 such as the Insecticons and the "Flyboys" like Skywarp, Thrust, and Derge, but they have heads like Shockwave.
Oh yeah, and sector 7 is in it when they spot BB crashing on Mars. Hope this helps. Its interesting to note that the preview picture for issue 3 is of Brawl shotting at Jazz on Earth, so I have no idea what issue 3 will be about.