Double-click on the drum track to replace to open it in the Sample Editor. Go to the Audio menu and select "Hitpoints/Calculate Hitpoints." Set the "Sense and Threshold" parameters to detect (and replace) the specific drum hits you want. For this you can use the presets or the manual "Advanced" setting.
Select "Create Markers from Hitpoints" to mark every drum hit your Sense and Threshold settings detect.
Close the Sample Editor and open an empty "MIDI Part" the same length of your drum track. Route the output of the MIDI track to your drum sampler. Open the MIDI Part for In-place editing by pressing "Ctrl," "Shift" and "I" simultaneously (or "Apple," "Shift" and "I" for Mac users).
Select a MIDI note to trigger your sample. Choose the pencil tool and draw a single note into the MIDI Part. Switch to the pointer tool, select the note you drew and cut it to the clipboard. Click the ruler in the Project Window to set the Project cursor to the near left of the drum hit you want to replace.
Press "Shift" and "N" simultaneously to move the cursor from marker to marker. Press "Ctrl" and "V" ("Apple" and "V" for Mac) to paste your MIDI note.