Display sale price only if the item is in stock using liquid rendering engine?

Question

Is there someone that knows the liquid rendering engine? Client meluka.co.nz wants the sale price displayed only if the item is in stock. LiveChat advised that this can be implemented using the liquid rendering engine so if the stock is greater or equal to one the sale price (discounted price) will show up. If no product in stock the retail price will display. Ad is in tomorrow's paper so pressure is on - urgent developer's help required please!
Individual Product - Large currently:
<ul>
    <div id="rrpprice_{tag_productid}">
    <h10>{tag_retailprice}</h10>
    </div>
    <li class="price"><strong>{tag_saleprice} <h9>(inc. GST)</h9></strong></li>
    <li class="quantity">
    <p5>Quantity:</p5>
    {tag_addtocartinputfield}</li>
    <li class="instock-message instock-{tag_instock}">
    <div>
    <p5>In Stock:</p5>
    <p2>Please allow 2 - 3 days (plus delivery)</p2>
    </div>
    <div class="no-stock">
    <p5>Made to Order:</p5>
    <p2>Please allow 4 to 6 weeks for manufacture (plus delivery)</p2>
    </div>
    </li>
    <br />
    <li class="quantity">{tag_addtocart,<img alt="" src="/images/btn-add-cart.gif" />}</li>
</ul>

Answer 1

Sure,
You see where I was coming from -"Can you do this for me for free" - I did Cringe.
But its straight forward. Liquid you have if statements..
http://docs.businesscatalyst.com/dev-assets/reference#!/liquid-reference/reference/logic-t ags.html
And you have your liquid tags:
Developer reference
{% if isOnSale == true -%}
DO THIS
{% else -%}
DO THAT
{% endif -%}
You need to double check as the old tag returned 0 or 1 and Liquid should be proper true or false, but not sure where BC got too in the constancy yet, they been quite on updates recently. If it does not work with == true then it will be == 1