All of the FEC filings of the Obama (and every other) campaign are available online. http://query.nictusa.com/cgi-bin/fecimg/?C00431445
You can wade through them to see how much was paid for legal services, especially since the election. I think the $2M figure is outdated by now.
There is no breakdown or itemization in these reports of what those legal services payments were for, so no one can say exactly how much was spent on eligibility suits. However, the amounts spent would be way out of the norm for any campaign, post-election, with the exception of Bush/Gore in 2000.
Thank you, ED!