Using e-cart 5 and powerstore 2 questions

hello i am using e-cart 5 and powerstore 2 and i am facing some issues...
I would really like some help from users that already have used these two products.

questions:
1. if i want to create new cart using e-cart, do i have to delete the default cart (WA_Store_Cart_PHP.php file) that is used in the powerstore and insert the new one? and how do i insert it?
I have tried to do some testings and found that after inserting a new cart, the code at the top of the cart.php file still requires the WA_Store_Cart_PHP.php file.

Are there specific steps that i have to follow?

Are there any chunks of code that i have to remove from the cart.php file after creating and inserting the new cart?

2. What is the purpose and function of WA_eCart_Definition_PHP.php file and how is it related with e-cart? When i make modifications to the cart file i have to also upload the WA_eCart_Definition_PHP.php to the server?

3. When i add a modified cart object to the cart.php file, are there any issues with the checkout page? I mean is there going to be some issues that i will have to take care of?


Any help would be appreciated.
thanks in advance