Re:"at least without hiring outside help" - (Score 2, Informative)

It might be a shameless plug, but Satchmo - http://www.satchmoproject.com is a completely open source option. It's not perfect (what software is) but I believe it is a much better alternative than most of the PHP based alternatives.

I am one of the core devs so I am biased but do feel compelled to chime in with an alternative to the PHP based solutions out there like Magento.