After either clearing out or avoiding the room full of new enemies, head into the hall from where they came and turn to the left. you will find a few creates of cash here. Now head to the right and search next to the air vent entrance for an audio log. Pick it up and then transform, heading into the duct and around the lasers in your path. Enter the next room search the back left corner for a blueprint, and then climb up the ramp of dirt to the next room. Transform to your vehicle form and drive into the air duct on the opposite side of the room. Take the right path to reach a secret room with an audio log, a Pulsar Cannon, and more crates filled with cash. When you've collected it all, head back into the air duct and take the other, left hand path to reach your objective.
You will find the switch in question in the center of the ring in the next room. Pull it an a large spire will emerge from the abyss below you, cloaking the room in the glow of foreign stars. A staircase will form at your feet. Walk up the staircase and you will see a projection of Earth floating in front of you. Apparently, this planet is a great fit for the Transformers, rife with Energon. Leave the staircase from the exit at the top and use the store in the next room if you need more upgrades, ammo or perks.
A small ramp will lead you down to the lower level. Head over to the left. You will see a group of seekers searching for you on the floor below, so get ready to fight as you make your way to the bottom floor. A lone Decepticon will patrol the hall in front of you. You can kill him silently if you are fast enough, but you can also opt to avoid him and duck into the air duct on the far wall. Unfortunately, this path is a bit more risky. You will have to pull the switch to the left of the guards and the air duct exit, and it's highly possible that the guards might spot you opening the door. You do have a chance of escaping as long as you are cloaked.
If you opt to kill off the patrolling enemies, you can use the air ducts to mount a quick retreat after offing one or two of the enemies with a stealth execution. Come out later, once the enemies have turned their attention elsewhere, and use your cloak to kill the rest one at a time. Once all of the enemies are dead, pull the switch to open the circular door ahead. Seekers will be searching for you in here. Duck off to the right hand outcropping in the hall and transform, driving into the air duct ahead. There will be two exits to the air ducts, one towards the front and one towards the back. The one towards the front is the safest to take. Cloak yourself and sprint as quickly as you can to the switch at the far end of the room. Avoid getting caught in the Seekers' beams at all costs; if you are caught, you will have to deal with a tough fight. At the very worst, you should try to sneak around cloaked and kill off the Seekers one at a time. At best, you can open the door without the enemies seeing you and slink away to the next room.
The next room will have more Seekers, along with regular Decepticons. Use the air duct to the side to get around them. You will emerge behind a lone enemy. Hit X to execute him, and then poke your head out through the doorway to see where the enemies are patrolling in the room ahead. With any luck, the Seeker will be facing away from you. If so, activate your cloak and run as quickly as possible through the doorway on the left, past the enemies in this room. If not, wait for him to turn his back and then slink away to the next room without initiating a fight.
In the next room, pull the switch to the left to open the circular door to the next area. Smash the cylindrical crate to get some money, use the store if you need it, and then proceed around the corner and into the next air duct. Head off to the left branch of the ducts to find a hidden room with an audio log and a few more of the cylindrical crates with currency in them. Grab it all up and then drive back into the ducts and proceed towards your waypoint. This will lead you out towards your next objective.
