Oscommerce Google Analytics Installation and fixes

We have one oscommerce website with Google analytics installed and it shows statistics fine but i want conversion tracking and eccomerce installed. I also have 6 other sites that need google analytics fully installed, all are oscommerce sites. If i am happy with your work then the work will be ongoing with 1-2 new sites a week. You must be able to install analytics properly so i can see where buyers came from, eg what keyword they searched or how they got to my site. Email me if you need more details, you must have done this before.