Wow - slow down there. Don't over react!!! Think you have several issues, but good chance that planaria aren't one of them!
First Google planaria vs. detritus worms. If you have Amazonia soil, then you almost certainly have detritus worms. They are not a problem, maybe bit yucky to see if you have too much, but realistically a natural and inevitable part of a healthy tank. Planaria have characteristic triangular shaped heads. Detritus worms don't (they can be thin white cotton stringy, or fatter, floating in water, on glass or in substrate). Whatever worms you may have, they're probably not what killed your guppies!
So you've put your filter in bleach? The filter media / sponge too?
That's not such good news as you've probably wiped out all the beneficial bacteria that your tank has spent the past couple of months building up.
So might need a bit of disaster management. Sorry to say that what you've done so far might have caused more problems than it has solved. But don't give up! We've all been there with our first tank. First step, don't add any more chemicals, bleach, salt etc.
Let us know where you're at with the tank (photos might save an essay) and sure someone can guide you how to get everything back up and running and solve any problems.
Good luck, don't despair, you'll have a great tank soon enough!
Kind regards, James