Whoops, been neglecting this a bit, haven't I?
Anyways, did the geth dreadnought. Basic gist of it is, a geth dreadnought that has been sending out a signal to make other geth more powerful, and Shepard is going in with Tali and one other (Garrus) to shut down the signal. Bringing Garrus along does lead to a very funny exchange where Garrus offers to share some dextro-friendly chocolate that Dr. Michel bought him. Completely missing the implications of Dr. Michel buying him chocolate. In Tali's words, "Watch yourself, Shepard."
There's also a funny moment near the beginning of the mission where Tali is complaining about once again having to go through vents. "You did fine on the Collector base." "I GOT SET ON FIRE!"
Anyways, this is a pretty basic mission overall. Get to the center core of the ship, shut down the signal emitter, get out. There are complications along the way, like the geth catching on and shutting down everything in a lockdown that is overridden by Tali creating an emergency situation to reverse enough of the lockdown to go through the battery of the ship, leading to a rather fun segment where you have to fight geth while taking cover to prevent the shockwaves of the BFG of the ship taking down your shields.
After that, and a near fatal elevator sequence that becomes somewhat funny if you are a Male Shepard romancing Tali where she claims she was only worried about her reputation if Shepard died because of her technical skills not being up to scratch, we reach the drive core, and find out the source of the code being sent out...Legion is back. He is willing to help you out, however, as he was against the consensus that led to the geth turning to the "Old Machines" for an upgrade in desperation when the quarians started attacking them. Problem is that cutting him out of the machinery manually will cause issues, so we have to do it carefully by shutting it down properly, requiring a bunch of running around. Still, success is had, and the dreadnought is no longer sending out the signal. That's the good news. Bad news is that the dreadnought was only relaying the signal, it wasn't the source of the signal itself. The worse news is that with the ship shut down, Han'Gerrell decides this is the perfect time to strike and blow up the dreadnought. With Shepard and a FUCKING ADMIRAL OF THE FLEET still on board. I'm sorry, I know we've addressed Han'Gerrell is rather bloodthirsty, but this is downright dumb. Anyways, cue Shepard and co, now including Legion, barely making it off the ship. To her credit, Admiral Raan did try to pull back and not follow through on the attack, but Han'Gerrell basically said "I'm doing this, and if you pull out, you'll divide our fleet and then who knows how many deaths are on your hands?", so she was forced to go along with it, although not without damning Han'Gerrell.
Back on the ship, Shepard did what pretty much everyone wanted to do and punched Han'Gerrell and told him to get the fuck off her ship. He didn't do that, but whatever, the punch was enough satisfaction. Anyways, after a rather tense meeting between the Admiralty Board minus Koris and Legion, Legion reveals that the signal source is on Rannoch, but there is also a server that will disrupt the geth and break their connection to each other to make getting to the signal viable. Meanwhile, Koris has crash-landed on Rannoch. So, three missions. Given that the server and signal aren't going anywhere, time to rescue Koris.
ETA: Oh, and Shepard basically said "We'll see" when Xen expressed interest in taking a...closer look at Legion once everything is taken care of. Yeah, felt a bit iffy, but Legion can always say no, and if he does, Shepard will back him.