Steps required to implement Konacart within a company’s existing website?

[Sumatra]

A mid sized company has asked me to develop a shopping cart application under a small budget.  I believe that I can provide a much more robust solution by customizing Konacart to run within their exiting web pages.  The company will not let me use the customer facing side of the shopping cart application as is.  I must customize it to run within their exiting web site and existing look and feel.  In other words they will provide an frame in the web page and the product display and shopping cart client must eixst within that frame.

The purpose of this posting is to identify the major actions that one must perform to implement Konacart for a customer who wants to integrate it with their existing web pages. 
Assumptions: 

1) Since the Konakart admin web application is not customer facing, it can be used without modification.
2) The company needs to be able to scale the shopping cart to handle a large number of concurrent buyers, so it will be implemented as a clustered application running under their JBOSS application servers.
3) The  Konakart database will be used as is under Oracle or MYSQL
4) The developer has experience with struts, and most of this company's java web application's are built around struts, so KonaKart is a good fit for this company.

Required Customization Tasks (Please let me know if I am leaving out any important tasks!)

Develop a JSP/Servlet to register customers using the application's API. (From the code samples, it looks like one does not have to register them before placing items in their cart.  The sample insert order API will let's one insert order's based on an order ID and the customer's session ID before they have to register.  But you must register them before processing their order.)

To integrate with the company's web site, a JSP or servlet will be developed within
a Frame that displays the company's products.

The KonaKart API will be used to do the following actions from the product pages to:
Add items to a basket
Get/add shipping address.
Get shipping quote and display it
Get order total and display it
Get payment information
(The functionality to search for products will be added later, as an enhancement) 

The KonaKart implementation must be customized to run with the company's payment gateway service, CyberSource. 

The KonaKart One Page Checkout will be used to do the following actions:

Allow existing registered users to login
Display to users a confirmation of their order and allow them to change shipping method, add a coupon code, and add comments to the order.
(It is not clear if this one page check out can handle cases of forgotten passwords. Can it?)

What customizations are required to set up shipping information to allow shipping quotes? Can setting up the shipping information (to obtain shipping quotes) be done through the KonaKart Admin application? 

Issues

The users must have already logged into the web site to access the product pages. They may not like having to do an additional registration step the first time that they order. To provide single sign on, it will be necessary find a way to pass the users email address and the fact they have been authenticated to the shopping cart. Double sign-ons and making the customer have two passwords - one for the web site and one for the shopping cart  registration - will probably not be acceptable. KonaKart uses the Java JSESSSIONID cookie to pass session information.  The web server uses a different technique for saving this information.
The web pages will be hosted on the web server, and the JSPs and shopping cart will be hosted on the JBOSS server.

Can you think of more items for creating a statement of work for the subject task?