replace instructions

Author: norareidy

source/usage-examples/replace.txt

@@ -26,13 +26,22 @@ Example
 -------
 
 This example replaces a document in the ``restaurants`` collection of
-the ``sample_restaurants`` database. The example uses a ``Restaurant``
-struct that has ``name``, ``borough``, and ``cuisine`` fields to model
-documents in the collection.
+the ``sample_restaurants`` database. The ``replace_one()`` method replaces
+the first document in which the value of the ``name`` field is
+``"Landmark Coffee Shop"`` with a new document.
 
-The following code replaces a document in which the value of the
-``name`` field is ``"Landmark Coffee Shop"`` with a new document. MongoDB
-replaces the first document that matches the query filter.
+You can access the documents in the ``restaurants`` collection as instances
+of the BSON data type or a custom data type. To specify which data type represents
+the collection's data, perform the following actions on the highlighted lines:
+
+- To access collection documents as BSON documents, replace the ``<T>`` type
+  parameter with ``<Document>`` and the ``<struct or doc>`` placeholder with
+  ``replace_doc``.
+
+- To access collection documents as instances of the ``Restaurant`` struct,
+  replace the ``<T>`` type parameter with ``<Restaurant>`` and the ``<struct or doc>``
+  placeholder with ``replace_struct``. The ``Restaurant`` struct is defined at
+  the top of the code file.
 
 Select the :guilabel:`Asynchronous` or :guilabel:`Synchronous` tab to
 see the corresponding code for each runtime:
@@ -47,6 +56,7 @@ see the corresponding code for each runtime:
 
          .. input:: /includes/usage-examples/code-snippets/replace-async.rs
             :language: rust
+            :emphasize-lines: 19, 36
             :dedent:
 
          .. output::
@@ -63,6 +73,7 @@ see the corresponding code for each runtime:
 
          .. input:: /includes/usage-examples/code-snippets/replace-sync.rs
             :language: rust
+            :emphasize-lines: 18, 35
             :dedent:
 
          .. output::