Woocommerce custom add to cart button with custom checkout page - php

Question

I have a Woocommerce store, I was looking to add another add to cart button named "Try now" to a particular category(not to all the categories). When the user clicks on "try now", it gets redirected to the custom checkout page.
On custom checkout page, try-now products can be added up-to 5 products max, total is fixed as 500 for all the try now products and payment only by card.
I have found the following codes.
Code to replace add to cart button
function remove_loop_button(){
if (in_array( 10, $product->category_ids))
remove_action(‘woocommerce_after_shop_loop_item’,‘woocommerce_template_loop_add_to_cart’, 10);
}
add_action(‘init’,’remove_loop_button’);
add_action(‘woocommerce_after_shop_loop_item’,’replace_add_to_cart’);
function replace_add_to_cart() {
global $product;
$link = $product->get_permalink();
echo ‘<a href=”‘.esc_attr($link).'”>Try Now</a>’;
}
And also this code to customize checkout page from Make 2 different WooCommerce checkout pages?
add_filter( 'woocommerce_checkout_fields' , 'custom_override_checkout_fields' );
function custom_override_checkout_fields( $fields ) {
global $woocommerce;
//assuming only one product in cart
foreach ( $woocommerce->cart->get_cart() as $cart_item_key => $values ) {
$_product = $values['data'];
}
switch ($_product->id) {
case '666': //product id for product 1
//do stuff with the checkout fields
break;
case '999': //product id for product 2
//do stuff with the checkout fields
break;
}
return $fields;
}
I know it's quite complicated, Can any one please suggest me where to start? Or any hint will be appreciated. Thanks.