virtualbox.org

Basically, I have my host vm (server 2008) connected through internal to my guest vm (windows 7.)

I need to have these two connected internally, and ONLY my server 2008 vm to have a 2nd network adapter (be it NAT or bridged), but the guest vm must also be able to connect to the internet despite only being connected through an internal network.

Any ideas?

You solve that exactly the same way as if it was a physical setup. Enable RRAS as a NAT router between the internal network and the external network.