QUOTE(ArcoJedi @ Jun 29 2009, 01:56 PM)
I don't know the answer to your question for definite certain, but if you have a sitemap that is already recognized by Google I'd keep it where it is. If the new sitemap you are creating with new products also has all of the same old products you can just replace it with the new one. This should only expand what Google knows about your site, and not drop your results for your current pages. However, everything I've read indicates that you can also just have multiple sitemaps referenced in your Google account. So either way will work.
Thank you, i was leaning toward keeping them both but was afraid of all the duplicate content stuff I hear. I dont know how to check if the URL's in the first sitemap are also in the second or how to remove the duplicated URL's so I wanted to make sure that I wouldnt get penalized for duplicate content in both sitemaps. Thanks for your help ArcoJedi!