Is it really bad if I have dupe content within my site? Like --- what if I have different content on each page but have the same paragraph on each page? I need to use it for description reasons..
No this is not a problem. Even a duplciate content is not such a problem if you add some value to it (more text content, graphics, etc.)
If you've your reasons to do this then don't worry. IMHO, it won't really matter. Also, the rule says make sites for people not for SE
As said by zexy, it should not be a problem as google will rank only that page which they feel is suitable but still avoid heavy duplication.
I suggest you try to avoid duplicate pages. A little bit of content on every page is however ok, but try not to put large amount of same content in different pages.
If you base every little thing on what you think "might" have an effect in a search engine you won't accomplish anything. Build your sites for your customers. The last stat I read stated only 11% of searchers even bother to go to page 2 in a search engine. They just research under new terms. So in any competitive niche there are only 10 spots to score. If you are unable to get in the top 10 then you had better figure out a way to get visitors that is NOT about SEO.' And that is the majority of sites. So do your best, but build for your customer so when you get only a trickle of traffic it still converts.
as long as you obtain 30-50% uniqueness, you are fine with the SEs. but again as advised by others, write contents for your visitors and apply also common sense. duplicate contents if properly used is not going to penalize your site as long as you maintain the uniqueness ratio required by the SEs