Short Version: What are the chances that a site's various sub-pages' page-ranks will suffer if a proper google sitemap is submitted for the first time?
Long Version: I'm working with a website that has some rather impressive organic page ranking on some of its sub-pages.
They've never submitted a sitemap to google, which has caused some of their primary sub-pages to be crawled rather infrequently (month-old data sometimes still shows on google search results, and a few of these are rather popular searches).
Furthermore, google still references some non-existing pages and visitors are visiting dead-links (I understand redirects would be ideal, where possible). The sitemap could let google know that those pages are no longer there.
Is there a way to communicate the information that can be communicated via google sitemaps without negatively affecting page-ranks throughout the site? I'm really concerned about shaking the boat too much and resetting some of the site's hard-earned Internet equity.