I've loaded these as NEW sitemaps as I felt replacing the old one wouldn't work given the numbers (suffixes) are different.
you would have to rename the new sitemap to sitemap.xml and replace the old sitemap with the new one for the old sitemap to be deleted.
In Google Webmaster, it has accepted every sitemap I've loaded, but the 'URL in web index' is nil.
Which means Google did not yet index any of your pages? Some of the pages are already indexed and do appear in Google (even if it says that there aren't any URLs in the web index). The Webmaster Tools are always a bit slower in displaying how many URLs are indexed. There's some delay.
Also it takes quite some time before the first pages show up in the index. Two weeks and more are not unusual. Google is slow in adding them in the index.