It can be done fairly easily - esp w/ clicker training. It does take time & lots of repetitons & patience. The first thing is to teach the dog to "drop it" on command - no matter what it is the dog has in his mouth. You start w/ trading for something better or else the dog has no motivation to give up what he has. You also have to teach the dog to consistently go to the designated toy box - always keep it in the same location. When these two behaviors are totally solid behaviors you have the dog bring the toy to the box, then later add the drop it command when his head is over the box. You have to teach each part separately, then add them together. The inclination is often to rush to the final trick but that will confuse the dog if the individual parts are not 100% solidly learned. Also, when he's learned the parts & the dog is ready to actually put toys away, have only the least favorite toys out so the dog will easily drop them - it's too much to ask that a favorite toy be put away. Later on, when he is good at putting away the boring toys, you can add the good toys.
Good luck. Keep us posted.