opencart COD extension edit and checkout page -- 2

max payment is 50$ !!!!!!!!!!! we use opencart 3 , with journal 3 theme we want 2 tasks : 1- edit the COD extension to be only for products we select means we need a select box in the extension page that shows all products of our store , the products we chose will be able for customers to checkout with cash on delivery we need also a fee option in the same extension page to add for those who select this method then finally , after finishing the order we have an api link to our shipping company , we just need you to make a variable in it to send total amount and order type to shipping company through the api to inform them of payment type ( will provide document ) only one line code for this 2- change the layout style of the checkout page to make it easier and simpler for customer to fell the data as quick as possible