I have been selling on E-Junkie for nearly two years now, and have personally done all the shopping cart integration into my e-commerce website. You can see how I integrated everything by visiting http://www.Pediasleep.com and taking a look at the individual sounds that my company sells.
Getting started on E-Junkie can have a steep learning curve that can leave you scratching your head and frustrated at times at the self-induced "snafus" you describe (been there, done that), but you are right that it's indeed "simple stuff" once you get the hang of it.
I would be happy to provide the "hand-holding" you are looking for, and take the time to walk you through the steps in a phone or web consult session. Compared with learning how to do it yourself though, I bet a consult would save you at least a couple hours of work.
Please send me an email by clicking on my user profile on the top left of this post, if you're interested.