Our version of the GA tracking code does not include optional extra functions such as AdWords tracking, and using other GA tracking code together with ours would create a conflict. You'd need to use AdWords tracking code that does not depend on GA tracking methods, though of course you can still integrate GA with AW at Google's end.
To add AW conversion tracking code to your E-junkie-generated thank-you pages, you can paste that in your Seller Admin > Account Preferences > Common Thank-you Page HTML field (to insert the same tracking code in every thank-you page we generate for you) and/or in the "Message (HTML)" field of individual products' settings (to insert code only when that product is purchased).