I'll spend my credits on a Javelin Gun, ammo and medkits. You can buy whichever you want, but i recommend medkits and ammo more than a new weapon already.
Shop till ya' drop
Next to the Store you'll find a Bench. You can use Power Nodes to upgrade your weapons, suit, and stasis. I recommend to save one node for unlocking special closets.
Keep moving till you walk into a room with a treadmill, and prepare to shoot a Necromorph that is sprinting at 20 mph to slice you.
Feel free to save!
This is why I recommended you save a power node. Closets like these can mean the difference between life or death, so always have ONE node.
Keep following your locater till you see a doomed woman, prepare for some necromorphs.
Aim for the arms!
After you head to the elevator you'll find this man being sloppily garroted by a failure of an assassin.
Stross will then proceed to spam Isaac with pointless facetime phone calls, after which a Leaper will pop out from the railings to try to eat you.
Fortunately, I smacked it away.
Proceed and you'll see a doomed couple running from a room that contains a Puker.
A slasher will also join the fun.
Reminds me of the Exorcist really, don't let that thing get close to you or else you'll lose half your health instantly from the puke.
After the Mother-in-Law has been vanquished, turn to see her special friend trying to put on her make-up (with your blood)
Whoops, she bit me. Every monster in Dead Space will do button sequences like these. Just mash E and hope that you don't get eaten.
After you head forward, the lights will dim and the doors will lock, prepare.
Slashers and Pukers will all pop out. Just aim for the arms and stasis when they get too close.
Keep heading forward and you may hear some nutjob yelling at you to go away, so might as well not mess with him (HE'S ARMED!)
Open your inventory. Move your cursor to the middle row.
Then move it down, Isaac will headbang. Proceed as many times as possible.
The Elevator will yield a save station which you should definitely use.
Proceed and more slashers will pop out.
Enjoy the "wow explushins" as people's lungs are sucked from their chests if they survive being turned to kibble from the explosion in a vacuum.
When you proceed to this second treadmill area, a feigning-death Slasher and Leaper will pop out to hinder you.
If you decide to not be 2spooked then keep moving forward and the doors will lock yet again. Turn around to the cries of yelps and you'll see some goddamn Exploders. I shot his arm off :)
WHAT YOU GONNA DO PUNK?
If you successfully shoot off their arm then you can use Kinesis to propel it to the faces of other Exploders (or slashers).
Exploders will also pop out from behind.
Once all exploders have..exploded, the doors will conveniently unlock and you can proceed down this ominous hallway where nothing creepy will happen.
Just joking, flashlight is here to illuminate your way.
Once you get near the train you'll see an Infector practicing necrophili---i mean making more Slashers. You can't shoot him past the glass, but if you see an unprotected Infector you should most likely shoot the shit out of it.
Head forward into the train and get into the crawlspace.
The train will start and Slashers will start popping out, keep heading forward into the train after the zombies stop coming.
These pukers will also be trying to get the jump on you. Shooting him in the chest will stop a puke.
Electroshock therapy can also stop his nausea.
If you manage to reach the end, Isaac will try to commit suicide...by getting to the other end of the train.
NO ISAAC, DON'T DO IT!
Isaac will then jump, control him with the arrow keys to get out of the way of these doors.
Then it'll start a button sequence to get you up.
It's not over though, once Isaac lands ass-first onto the metal floor, more zombies will come to make your day.
The train will then lurch and Isaac will fall again, ass-first and begin to slide. You don't need to shoot anything on this part, so save ammo for what's going to come.
Don't be as stupid as me, using the Javelin Gun on this part is suicide. Don't bother shooting the necromorphs, either.
Isaac will then hang, and Slashers will come.
First, some slashers, then exploders. Then LOTS of slashers. Don't let them get to you.
If you survived the slashers, you'll hear a horrendous screech and turn to see a zombie gorilla trying to mess with the train. Shoot his arms to end his efforts.
Once he's lost an arm, Isaac will then GTFO of there.