Find and replace text in all posts in Vb5х

[Pompadur]

Hello! Need help!
For finding and replacing text in Vbulletin 4 i used this Hook:

Product : vBulletin
Hook Location: postbit_display_complete
Execution Order: 5
Plugin PHP Code:
$search = 'xxx;
$replace = 'zzz;
$this->post['message'] = str_replace($search, $replace, $this->post['message']);

And it works!
But i don't know how to do the same in Vbulletin 5

As i understand i need to go to Admincp > Products & Hooks > Manage Hooks and click the link that says "[Add New Hook]"
Product : vBulletin
Hook Location: conversation –reply_threadview_text_1
Execution Order: 5
Template Name:

As i understand i need to create a new template, for example «conversation_replacing»
But what i should do to make text from the post go to str_replace()?
What i should mention in "Hook Arguments:" to make the hook work?

Please if you know how to do it - explain step by step, i 'm very new in this area.

Thank to all!
PS Sorry for my bad english!