Not hard. Take the cover off at the bottom of the bell housing and turn your engine over by hand until the screw heads appear. Check to see if they're tight and turn each screw until it is. If they're tight but the flex disc is loose, it may be that the screws are too long and they're bottoming out in their respective bores. Replace the screws with slightly shorter ones or add a washer. A loose or broken flex disc will make a lot of noise.
I've also had one where the actual disc was cracked but in that case the noise was really only there at idle and it would go away at road speed. If that's the case, you will have to remove the trans to replace the flex disc.