Silentthread, you can make that repair. (on a scale of 1-10 for a DIY, maybe a 2-4). I would replace the Fill Valve & Flapper, just read the instructions carefully. Retighten the tank level ( Nut tighten counterclock wise). Before any plumbing repairs, make sure the shutoff valve is working properly. If you have any question, someone here will be gald to help. good luck.