I recommend that you use PSG-1. It can kill in a single shot with lower price if you play PSF...
Well, you start it off the Ijji Reactor. Log in from that, go to "Soldier Front" In the Ijji Reactor, and click start/download.
Pixi already answered the first. But if you are a newb I'd recommend the M4A1. Low recoil and easy to play with. And also the PSG-1. Good sniper for starters and it's been held down by Pros. You rarely see other kinds of snipers.
Well the gun I'd recommend is Psg-1 !, It rocks dude. But it's your choice.