Here's a little tip that makes things a little easier when adding a sample to a snare in PT.
Copy the new snare sample in to the copy buffer. Create a new track for your sample and place it
above your original snare track. Group the new snare track with the original snare track. Use "tab to transient" on the original snare track to locate the snare transient and then push V on your keyboard. The new sample will paste onto it's new track without doing anything to the original snare track. Make sure that the A-Z is on ( to the right of the "tab to transient" on/off button).
David Reitzas : Mixer - Engineer - Producer