Userscript for deleting/changing site objects?

Question

userscript

There is some site, in the source code I change everything that I need (some objects).
We need a user script that would replace some lines in the source code when updating the site. In my case there is a spoiler of this type

<div class="toggle">
<div class="title closed">
<img class="titleIcon" src="/images/icons/dark/pencil.png" alt="">
<h6>Информация о займе</h6>

<div class="date"> 24/05/2015г.</div>

<div class="buttons">
<span>Активный</span>
</div>
</div>
<div class="body" style="display: none;">
<fieldset style="width:100%" class="blank_info">

<div class="formRow last">

<div class="formRight biger">



<span class="oneFour" style="width:130px;">
<span>«03» 06 2015г.</span>
<br>Дата истечения </span></div>
</div>




</fieldset>
</div>
</div>

You need to <div class="date"> 24/05/2015г.</div>
add text with <span>«03» 06 2015г.</span>
to get something like this

<div class="date"> 24/05/2015г. «03» 06 2015г.</div>

You need a chrome script.
There are a lot of such spoilers on the site and I need that for each spoiler in the "date" it was written exactly from this spoiler.
This is necessary in order not to open each spoiler, so to speak, so that the necessary information can be seen without opening the spoiler.