As this is a squad based mission you'll want to use the attack-move order a lot when you're getting around. I don't recommend using the stim packs ability at all because it will hurt your units. Seriously, you're better off without it as if you lose a unit it's not coming back. When you've got your units in a group head to the northwest. The door should open automatically. Follow the hall. Pass up the door on your left as there's nothing there for you but some civilians you can slaughter. On to the northwest you'll come to three options. Into the door or to head to the northeast or southwest?

Honestly it's not very useful (I recommend you do though) but you can go to the northeast path and follow it to a beacon to teleport to another room with two beacons.Kill the lone guard here then step on the other beacon. It will activate some security cameras so you can see some of the area. Not very useful eh? Ok. Now go back. The doors and the southwestern path lead to the same place but the southwestern path is safer (there's a goliath behind the doors which will attack you). Follow the southwestern path and you'll come near a room that was highlighted by the security cameras. Enter it, kill the marine here then step on the beacon to deactivate the security in the area. No more of those floor guns will attack you! Ok. Now move to the northwest toward the next beacon. Step on it to open the cell doors. Kill the zerglings in the northwestern room. You didn't have to do this but since there's dialog I figured you should. Now go back to the last intersection. Take the northeastern path this time.

This path is long and leads you far from where you probably expected you'd go. Be glad you turned off the automated security or you'd probably be attacked here. When you reach the room with the steel doors don't enter them. There's nothing but two vultures in there who will attack you and probably do some damage. Head up the stairs and onto the beacon. You'll teleport to 'sector 1' or as I like to call it, the northeast corner of the map. In the southeast of this big room is a door and there are actually two floor machine guns here (don't know why) but they should be eliminated quickly. Head through the door then follow the path. There are minor enemies here but you should be fine. You'll finally come to the door with the computers. Kill the ghost and two marines who are guarding it then step on the beacon to end the mission.