How to override an extension admin template

Question

There is an extension which I want to add a little more features on. To achieve that I need to modify two .phtml files in

app/design/adminhtml/default/default/template/Orderpreparation/Packing/Index.phtml app/design/adminhtml/default/default/template/Orderpreparation/Packing/Products.phtml

I found that Index.phtml is mentioned in

app/design/adminhtml/default/default/layout/orderpreparation.xml

<?xml version="1.0"?>
<layout version="0.1.0">
    <adminhtml_orderpreparation_packing_index>
        <reference name="head">
            ...
        </reference>
        <reference name="content">
            ...
            <block type="Orderpreparation/Packing_Index" name="onepagepreparation" as="onepagepreparation" template="Orderpreparation/Packing/Index.phtml">
            </block>
        </reference>
    </adminhtml_orderpreparation_packing_index>
</layout>

On the packing page in the admin, selecting an option in a dropdown list with trigger Products.phtml to be loaded via AJAX and I can't find anywhere of triggering the Products.phtml.

If I want to override Index.phtml should I just create an xml file in layout folder as below:

app/design/adminhtml/default/default/layout/my_own_xml_to_override_index.xml

<?xml version="1.0"?>
<layout version="0.1.0">
    <adminhtml_orderpreparation_packing_index>
        <reference name="content">
            <block type="Orderpreparation/Packing_Index" name="onepagepreparation" as="onepagepreparation" template="MyOwnFiles/Packing/Index.phtml">
            </block>
        </reference>
    </adminhtml_orderpreparation_packing_index>
</layout>

Do I have do anything else to make sure Index.phtml will be override by my own phtml?

No idea how to I setup to override the Products.phtml?

Do I need to create a new extension in this case?

---

I created my own extension and below is the config.xml

<?xml version="1.0" encoding="UTF-8"?>
<config>
    <modules>
        <Company_ErpFlyerReminder>
            <version>1.0.0</version>
        </Company_ErpFlyerReminder>
    </modules>
    <adminhtml>
        <layout>
            <updates>
                <flyerreminder>
                    <file>packingflyerreminder.xml</file>
                </flyerreminder>
            </updates>
        </layout>
    </adminhtml>
    <frontend>
        <layout>
            <updates>
                <flyerreminder>
                    <file>flyerreminder.xml</file>
                </flyerreminder>
            </updates>
        </layout>
    </frontend>
    <global>
        <blocks>
            <flyerreminder>
                <class>Company_ErpFlyerReminder_Block</class>
            </flyerreminder>
            <adminhtml>
                <rewrite>
                    <packing_index>Company_ErpFlyerReminder_Block_Packing_Index</packing_index>
                </rewrite>
            </adminhtml>
        </blocks>
    </global>
</config>

app/etc/modules/Company_ErpFlyerReminder.xml

<?xml version="1.0"?>
<config>
    <modules>
        <Company_ErpFlyerReminder>
            <active>true</active>
            <codePool>local</codePool>
            <depends>
                <MDN_Orderpreparation/>
            </depends>
        </Company_ErpFlyerReminder>
    </modules>
</config> 

app/code/local/Company/ErpFlyerReminder/Block/Packing/Index.php

<?php
class Rycomau_ErpFlyerReminder_Block_Packing_Index extends MDN_OrderPreparation_Block_Packing_Index
{
}

Answer 1

You have defined your adminhtml layout xml with name packingflyerreminder.xml

Create a file app/design/adminhtml/default/default/layout/packingflyerreminder.xml with below code

<?xml version="1.0"?>
<layout version="0.1.0">
    <adminhtml_orderpreparation_packing_index>
        <reference name="onepagepreparation">
            <action method="setTemplate"><template>MyOwnFiles/Packing/Index.phtml</template></action>
        </reference>
    </adminhtml_orderpreparation_packing_index>
</layout>

Now create your phtml file at app/design/adminhtml/default/default/template/MyOwnFiles/Packing/Index.phtml with your custom code.