URL formatting... Should I worry about Duplicate Content

I decided to generate my urls in the form of
.com/article.php/1234-43/-title-of-the-article-goes-here

Where 1234 is the id of the article and 43 is the "section" or "category" that the article resides. An article can be in multiple categories. The tail is just to give some regular english to the url (and perhaps score some SEO points).

What are your thoughts on this format?
It is possible to have the exact same article have a different url with the only change being the category id (the "43" for example might be "31") the page changes slightly but its basically the same. The theary is that some category classifications are more suitable than others so I can utilize the best category in the url when passing the link around. BUT I also want the article to show up in other categories when users are browsing by category.

Would I get penalized for duplicate content?
Is there a better way to do this or is acceptable?
How about the keywords at the end? Is this good or bad? What should the limit be for the number of words I use?

Currently, the site does not have many credible inbound links and most pages show up in the supplimental index only (probably do to the low inbound link rating).
The site however is ranked in the top 30,000 in Alexa (ok, I know its pointless but still..). PageRank on the main index page is 3

Thanks for any comments or suggestions
- John

I think duplicate content will be an issue here.
You can try to make the page more unique in other categories by adding more category information for example (and change title, meta etc).
Keywords in the url are good practice. I always try to keep a max of 4.