dude.. I will help, as will others but you need to go off and find tutorials to get a bit of understanding..
To explain even the most 'simple' things (like skinning those bunkers) still opens up a can of worms. Its only simple on the basis you understand other things.
I forget how I leant max but it defo started with a lot of messing around in max, pressing buttons and trying stuff.. then gradually some things make sense with others.. once you start to get that understanding you will have more specific questions that can be answered here.
for the record.. although it looks a bit mental..

that gun attempt is actually kinda good in many wasy.. keep at it.
And on the poly count/server lag... its all about collision mesh.. I have 12mb 40K poly mesh files running in bf42 just fine.. the gun models dont have collision mesh so its not an issue.