Your question is not clear. Is it the wording that you want to change, or is it the positioning, or styling that you want to change?
When you changed the text in the Thank-you.php page I hope you didn’t make the change in the original plugin. You should make a folder called woocommerce in your theme folder, copy any of the plugin’s files that you wish to change and paste them in there. Then only make the changes on the copied files. Woocommerce know to look there for files first, and then if they can’t find them, they go to the original plugin folder.
The wording is in templates > checkout > thankyou.php.
On line 38, you will see the code where this text is set:
<p class="woocommerce-thankyou-order-received"><?php echo apply_filters( 'woocommerce_thankyou_order_received_text', __( 'Thank you. Your order has been received.', 'woocommerce' ), $order ); ?></p>
In your woocommerce copy that you made in your theme folder, change the text here, and your website should pick it up instead of the original text.
Give me a bit of time, and I will set up a demo for myself and do a bit of experimenting. It could be the way you set up the ‘child’ folder for woocommerce, but you said that the other change you made worked out okay.
I’m sure it can be done using JavaScript. I don’t have that strong a background in JavaScript to be able to help you, but I’m sure there are others here who could.
But I’ve found that if there are changes to be made, chances are other people have tried and asked about them before. So I would suggest also that you search in the WooCommerce or WordPress sites for similar situations first.