StaceyR

It looks like the answer offered hides the Add to Cart, and the Price as well. If you only want to hide the Quantity input field but keep all the rest, you can add this to the custom CSS editor:
.product-quantity-input { display:none !important; }
This will affect products site wide, so if you need this for only a specific product page, you can add this in style tags via the page header code injection:
<style> .product-quantity-input { display:none !important; } </style>

Try putting the below in the order confirmation code injector instead.
<div class="redirect-text"> <h2>Thank You for your Order.... onward to the the General Info Page!</h2> </div> <script> $('.redirect-text').insertAfter('#confirmed-page'); </script>  

Sorry, I forgot that you will also need to load the jQuery library as well for that to work. You will need to add the below to your websites global code injector header.
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js"></script>  

I picked the best possible time to ask this question, right? Hopefully, Squarespace w/b up soon.
 

I think Squarespace is down which is why we're getting the 503 message. 
As for the redirect message I do know how to do this I will just need to wait for Squarespace to backup and running. Did you still want the order confirmation information (order number, total...) to still display or would you prefer for this to stay hidden and just display the message?

When you add a meta refresh statement to Settings > Advanced > Code Injection > Order Confirmation Page you can choose the delay before the page will redirect. 
For example, the zero in this statement will cause it to redirect to the selected page (www.squarespace.com in this example) immediately. 
<meta http-equiv="refresh" content="0;url=https://www.squarespace.com/" />
Whereas in this statement, the '5' will cause it to redirect after five seconds.
<meta http-equiv="refresh" content="5;url=https://www.squarespace.com/" />
Changing it to 10 would delay the redirect for 10 seconds and so on.
                                                      Did this help? Please give feedback by clicking an icon below  ⬇️