Worried before submitting...

[liquidblue]

  We have a strong SEO presence now with a 7 year old site...
Without ever submitting a sitemap using Google Webmaster tools directly, we have been doing great all these years with just search bots crawling our links as is.

I have installed the full version of sitemap generator and things look great.

Question: I've heard by finally making the submission our current page rank and urls may be lost after a submission?
                 Can someone attest that this wont hurt but submitting the sitemap?

[XML-Sitemaps Support]

Hello,

submitting sitemap will not hurt the indexing of existing pages in search engines, it will just help SEs to find other pages on your site.