Adding e-commerce functionality to existing web site

This is a short term project to add e-commerce functionality to a fully functional existing web site. We are expanding our scope to sell related products, need to make 1) landing page changes 2) add preferred products/services - all images, description, rights and formats are already acquired. In most cases, it will be copy & paste approach to clone the existing web sites selling the same products 3) Incorporate PayPal and 2CO on a typical PHP/MySQL web site/interface 4) Update Terms & Conditions and include Privacy policy and Return policy 5) Create a seamless 3-page checkout action, along with automatic email communication to arrange for drop-ship of checked out products We have around 20 products that we would like to add to our launching inventory. Product descriptions and details are readily available. What we need to know from you is 1) Share your previous experience working on similar projects, any working examples preferred 2) In order to add 3-page check out approach how many hours of work do you think is needed with which we can launch the business 3) Share your experience, if any, in internet marketing areas in selling products to end user customers Depending on the growth and relationship, this may turn-into a long term maintenance project, please keep that in mind so you can support this on an ongoing basis. Products and services are related to Medical/Health care/Senior care services - any previous experience in this niche is desirable.