What would I need to compile this using the 2006 libraries so it would work with my version? (or is that even the best route to take?)
I believe you would need VC++2002, which is fairly difficult to lay hands on these days (unless you have an MSDN subscription). You might be able to find a copy on Ebay. However, there are better (in my opinion) options.
Apparently, the DWGDirectX libraries, from the Open Design Alliance, expose the functionality you need, per the page DGC linked to. If this is part of a larger project with much of the code already written, I would chose this option, though it does add a large dependency to your project. However, if you plan to distribute the code outside of your organization, this option will most likely throw a monkey wrench in your plans.
The most direct and accessible route would be to switch to .NET, but I realize that might be a tall order if you already have a lot of code written.