wheel - 6:57 pm on Feb 23, 2011 (gmt 0)
I've added 5 to 10 thousand pages at once on to sites with about 10 pages. Didn't notice any problem. In your case I might suggest doing it in two stages set apart by a couple of months.
I also later removed that content with no ill affects either.
Google has publicly stated that you should be fine within limits. I don't recall their exact terminology, but my spidey senses are tingling suggesting that you're probably on the edge - thus my recommendation to break up the release.
Now,that being said, I'm working on releasing 50,000 pages of content on a brand new site. I expect to release them all at once. But that site is intended as a link magnet only, I'm not specifically driving for SE traffic.