ah young padawan, so many questions :-)
an RSS feed is basically just a stream of data - it is the software you use to display it which decides how it is laid out. A lot of the time people use Wordpress and there are lots of things you can do to customize the way the feed looks. Once you have the RSS feed syndicated into your blog, go into the Syndication settings for that feed and change what you want.
Make sure you ONLY use morphing RSS feeds - then your posts won't be the same as anyone elses and you won't have to worry about duplicate content penalties.
Again, in the wordpress syndication settings for that particular feed you can set whether to use the original posting date (i.e. when it was posted to the feed by its author) OR if you want to use the syndication date (i.e. the date it goes live on your blog).
?[Luke:] I can?t believe it. [Yoda:] That is why you fail.?
