Can I reset a user's password using the Firebase Admin SDK for Node?

It depends on which definition of 'reset' you're using.

If you mean reset as in 'change', then yes - the updateUser function allows you to provide a new password. See the following example from the docs:

admin.auth().updateUser(uid, {
  email: "[email protected]",
  phoneNumber: "+11234567890",
  emailVerified: true,
  password: "newPassword",
  displayName: "Jane Doe",
  photoURL: "http://www.example.com/12345678/photo.png",
  disabled: true
})
  .then(function(userRecord) {
    // See the UserRecord reference doc for the contents of userRecord.
    console.log("Successfully updated user", userRecord.toJSON());
  })
  .catch(function(error) {
    console.log("Error updating user:", error);
  });

If, on the other hand, you mean reset as in 'send a password reset email', then no, there doesn't seem to be a simple way of doing so via the Admin SDK.

Yes, you can. To generate a password reset link, you provide the existing user's email. Then you can use any email service you like to send the actual email. Link to documentation.

// Admin SDK API to generate the password reset link.
const userEmail = '[email protected]';
admin.auth().generatePasswordResetLink(userEmail, actionCodeSettings)
  .then((link) => {
    // Construct password reset email template, embed the link and send
    // using custom SMTP server.
    return sendCustomPasswordResetEmail(email, displayName, link);
  })
.catch((error) => {
  // Some error occurred.
});