i doubt that youll get free code on weapon spawning, but there are really generous ppl here. as for locking guns on the screen, position the gun where you want it, rotate it to get it to face away from you, then use the lock object command. heres some code from my game that you can use (note you may need to change the positions and scaling sizes for your guns as this isnt a standard way of doing it, and the gun is clipped for some reason and im trying to fix it):
load object "models\assaultRifle.x",1
position object 1,0.5,-0.2,1.
scale object 1,2,2,2.5
disable object zdepth 1
lock object on 1
coffee + monkeys + creativity = games