i can't get passed the alian part can anyone help

The "Invasion of the Yokel-Snatchers" level? From the start,hop onto the truck's roof as Bart and use your slingshot to pick off the aliens from a distance.Then as Homer,use the Helium container to get past the Duff trailer and take down the aliens in there and as Bart,climb the truck's fence and jump down the other side.Then move ahead and kill the next bunch of enemies (be careful,as one of them fires a laser).Then use the Helium Homer ability and glide to the other side of the street and fight the rest of aliens,then pull the lever to activate a sewer smokestack - change as Bart then glide to the pile of smoke and land into the other side.Then get to the wrecked store's carpets to watch a cutscene:welcome to the alien spaceship.Now,you'll see that guy Cletus trapped in the desk:pull the lever to save him.Now this is when the battle has began:you have to destroy the alien spawn machines to gain access to the main console.Use the Homer-Ball and rush to the vertical ramps to wreck the red beacons until they're all destroyed.Pull the boxes' levers to make hamburgers come out of them to keep your Homer-Ball energy up.Cletus is an ally since you helped him - he'll be carrying a shotgun,so if he's cornered, help him out.Now that all panels are down the main console is out:press the red button and that's it:alien invasion screwed!