MarketPress - editing inventory post launch

Hi,
I've been using MarketPress on an e-commerce site and generally I pretty pleased with it http://www.guisegifts.com/
However, it would be useful to know how to edit the stock levels and sales after launch, as these weren't uploaded correctly, i.e. stock levels were set to a generic 100.

I look forward to your thoughts.

Regards,
Nathan