This level is essentially one long, optional side quest. After a brief tussle with some smaller hives and one data post, you'll enter a large, empty area that happens to be the home of a shockingly huge snow worm. Your best bet is to avoid it and run through the snow towards the far side, but if you're feeling brave, bagging the worm can get you 50 more achievement points. Before you pass the steel wall and activate Mr. Worm, however, grab the two letter tokens near the beginning of the level. One is just behind the first data post, floating on the backside of one of the small huts, and the other is behind the dividing steel wall. If you're staring at the wall, the token would be to the left. Ignore the smaller Suits - the worm isn't going to let them through.
Your best friends in this grueling duel are rockets and disk grenades, both of which are strewn about the plains. The worm's glowing weak points need direct rocket hits (or a crapload of bullets) to pop, but a relatively on target disk grenade can tear the spots wide open. Stay close, otherwise the worm'll use an ice breath attack that knocks you around. If you're near it, the worm will either lunge at you after swaying its head side to side or fire missiles from its tail. Either way, wait until its attacks are over and then move in. It will take a long, long time, but eventually, the worm will fall. Just be sure to hit all the data posts on the plain (one of which rests near a letter "E") and once the worm is gone, stick to the west cliff for the letter "A." Again, if you're not into taking out the worm, just keep moving.
On the other side of the plain you'll see a large collection of junk, with one tower-like piece jutting into the sky. If you look really, really closely, you'll see the letter "G" floating at the top. It's a hard shot to make, but zoom in a bit and you should be good. Also, there's a staircase off to the side, near two T-ENG towers and a data post. Look at the base of the stair platform next to the towers for the last letter token.
After walking near the dilapidated building by the "G" tower, you'll watch a cutscene and get into a VS brawl. Hop into one quickly and start blasting away. This purple VS is fast, tough and carries a laser that tears the hell out of everything. But, there's a trick - once you see the VS' laser turret open (it's on the right), leap in the air and start hovering to avoid the blast. Or, if you're a bit more daring, just shoot a rocket at the VS to knock it back and cancel the laser. If your initial VS is downed, hop into one of the many others lying around.