I JUST DID IT!!!!!!
Oh yea, beat the level, if anyone needs any help with it just post right here and I will tell you. I really discovered a foolproof plan. And the mortar part isnt THAT hard, it took me 4 tries to do it, you just have to aim down and keep hitting those trucks and stuff. Also you are invincible while shooting/reloading, and you can drop off the thing at any time if you are about to die.