For carving the vents you can use any pointy blade.Hey ZMan, my friend printed the case last time I wrote here but since I have no budget to build it didn't post the photos. I just peel off the uncessary plastics on the edges, however the quality seems subpar. I don't know much about 3D printing maybe his printer is not that top quality and also he forgot to write precisely some of the vents. How can I carve those vents? Anyway, here are some photos;
Your CPU side panel seems to be printed with "Support type: Everywhere". What you see in the vent holes is "support material". It is meant to be chipped away. I've designed both cover panels to be printed with "Support type: Touching build plate" or without support.
The whole print seems to be a bit over-extruded. I guess you will have issues with the "piano hinge" that connects the cover panels to the skeleton.
I do not see on the pictures provided, the elements from bits.stl file. You will need them to mount the computer parts to the skeleton.
Let me know if you have ant additional questions.