step 1: take off the device's back panel using a guitar pick
step 2: remove the speaker module (2 or 3 screws)
step 3: unplug the screen cable
step 4: unglue and remove the broken touchscreen using a hairdryer and a guitar pick
step 5: connect the new digitizer and test it properly (this step is EXTREMELY important: I bought the digitizer that doesn't fit)
step 6: if everything's all right, use double-sided tape to glue the new digitizer
step 7: put speaker and back panel at their places