DOCS-268 edits to proc for replacing a replica set

Author: Bob Grabar

source/administration/replica-sets.txt

@@ -129,14 +129,18 @@ directly.
 Replacing a Member
 ~~~~~~~~~~~~~~~~~~
 
+Use this procedure to replace a member of a replica set when the host
+name has changed. This procedure preserves all existing configuration
+for a member, except its hostname/location.
+
 Replacing a member is useful if you have an existing configuration
 and only want to change the hostname of a member rather than completely
 remove all configurations related to the existing/previous set member.
 
 Use :method:`rs.reconfig()` to change the value of the
 :data:`members[n].host` field to reflect the new hostname or port
-number. The :data:`members[n]._id` field does not change as a result of this
-operation.
+number. :method:`rs.reconfig()` will not change the value of :data:`members[n]._id`. 
+
 
 .. code-block:: javascript