If its any help, I only knew a little html and css (basics).
I started playing about with zen about 3 weeks ago and started to build a proper fully functioning store last week and I might be a little biased here but I think it looks superb.
Ive ran into very basic problems along the way that has took hours to sort out (sometimes days), but now I know what the problem was, it all seems like it was over nothing. ie, something very simple.
I know the next one I decide to build will only take a quarter the time (still not finished this one yet).
My next big hurdles are incorporating a payment system and uploading and configuring to a server, the rest is mostly tarting the site up and cosmetics.
No doubt I will be tearing my hair out for a couple more weeks but Im confident I will sail through the next one in comparison and I will have saved myself thousands in the process.
Its well worth teaching yourself.