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Not sure this is the right category for your question but anyway here we go...
This is my view on things from a SEO perspective (it seems like you know quite a bit anyway but might be nice to get it confirmed)
1. Static URLs are always better for the search engines (has your SEO guy implemented any sitemaps?)
2. Unless you are going to use the old URLs again always use 301 redirects, permanent.
3. When you launch new pages you can be down-weighted a while until the new URLs have been 'validated' however if the engines cannot see your new dynamic URLs then it won't get back in the index
4. Relevant keywords in the URLs are always good as it helps the search engines to determine relevance
5. If you use a CMS that produces dynamic URLs you could consider Mod Rewriting or just install something that generates static URLs
Hope that helps a little bit
The majority if not all the peole i have met within SEO agree that static URLs are more SE friendly and can go some way to helping rank.
While there are not enough parameters to prevent a search engine indexing dynamic URLs, static URLs can contain targeted keywords that can increase visibility and click through rates as consumers can clearly see what the content of a web page is about. It is believed that Static URLs are typically ranked better in search engine results pages and they are indexed more quickly than dynamic URLs.
Also, unless you do intend to use the old URLs 301 permanent redirecst are always better.
Hope this helps