I'm skilled webdeveloper and webmaster, i have strong knowledge of Magento, and i will gladly help you resolve this issue. I'll need list of pairs bad sku, good sku (for example in excel, where one column is wrong sku, second good sku). The Magento dataflow import/export is wrong idea, because sku is identifier for products, so you can't change it that way AFAIK. However i can create custom script to do this job for you. I'll require temporary FTP login to get this job done. Please feel free to ask me any question or to send me more information by PM, thanks. I'm looking forward to our cooperation.