First off welcome to the boards! Pull up a chair, and join in the fun (madness?)
First make sure the gun is unloaded. We don't want to loose a new member so soon! To change the butt stock, you will need to remove the two screws on the recoil pad (rubber thing) then take an ultra long standard screw driver to unscrew the long bolt that holds the buttstock on the receiver. As for the foreend, the only way I know how to remove it, is to remove the entire slide.
This may be a little more than you wanted to do, but it will help you out later on. First, unscrew the magazine endcap, and remove the barrel. Look at the receiver on your gun, and you will see two pins above the trigger area. Punch these out all the way, and the trigger group will pull out. Now pull the slide back, and push it back foward with a little force (pretend you are jacking a shell in it. Three things will happen, the bolt is going to fall out, the bolt carrier is going to fall out, and the slide is going to come off. Put the other parts to the side, and focus on the slide. You will notice on one side it has two long arms. Leave that side alone, and look at the other side!
The large ring in there will have two notches cut out in it. That is what you want to unscrew in order to get that piece of the stock off. Once the new one is on, screw the ring back on, and we will start putting this thing back together.
Put the slide back on the magizine tube, and wait. Now I'm going to give you a little puzzle! If you pick up the bolt carrier, and look at it you will see it has some notches cut out. Let's see if we can figure out how it seats onto the slide. The "stair step" side should face up, and the highest step should be towards the front of the shotgun. Now, pick up the bolt, and place it, with the face of it, towards the front of the rife. Leave these parts on the slide, and we will put it all back. Line up the arms of the slide, with their holes in the receiver. They don't fit do they?
Reach inside the receiver and push the little metal arm that is on the right side in, and pull the slide in A LITTLE WAYS!!!! Now with a little preasure on the slide still, push the other metal arm on the other side of the inside of the receiver. The slide will now slide all the way in. Now, put the trigger group back into it's spot. It may need a little tap from the palm of your hand to make it seat right. Grab the two pins that we removed earlier, and put them back in place. NOTE: One pin is smaller than the other one, make sure they go into the right spot. Lightly tap them, and they will seat, and lock back into place. With the slide about 1/2 way open, put the barrel back on, and screw the magazine end cap on tight.