5. Bake! Everything should be ready to go. A couple important things to note: you should make sure you are using regular cameras to preview the lighting. You can use vray exposure control to match a vray cam exposure so that it works with Render To Texture. Also make sure you're baking your gamma into the render. For me, this is simply changing my color mapping mode to 'color mapping & gamma'. Also make sure output gamma is 2.2 (these settings might be different depending on how you render, test with a single object until the baking matches a vray render)
In the Render to Texture panel, check 'color mapping' & select the desired elements to bake. I currently I only bake with the VrayCompleteMap.
note: vraydisplacement wont bake out, so you'll need to place the texture being used into an actual displace modifier, subdivide the geometry, then collapse & optimize the geometry to be suitable for baking.
6. Export. Prep the file for export once everything has baked. If I net render the baking, I'll run the Render To Texture on my local machine with 'skip existing files' selected. At the point, I'll also choose under Baked Material 'Save Source/Create New Baked (Standard:Blin), and set the target map slot to diffuse color. Note: setting the wire color of all the objects to white before doing this will set the ambient color of the Blin material to white, which will make things easier in Unity when imported)
Run the bake again. It will skip all the objects since they've baked already, but it will put the textures into standard materials. I'll also click 'Update Baked Materials' for good measure. Then select 'keep baked materials' and clear the shell. Now you're left with a scene that has all standard materials, with white diffuse color, and the baked texture.
Optional: At this point I also use a script to load the diffuse textures into the viewport so they're visible. http://www.scriptspot.com/3ds-max/scripts/turn-viewport-maps-onoff
Shuffle the baked UV (10, or whatever channel you used), into channel 1. Channel 1 is the UV channel Unity uses.
Now you can export everything as an FBX. Note: I embed media, and for units scale I uncheck automatic and set it to centimeters.
7. Import into Unity! The FBX should load automatically if you export it into your Assets folder. The model should also have all the baked textures on all its materials. The shaders will be default Unity diffuse shaders. I use this script that my friend made to select all shaders and switch them to unlit/texture. UnlitDefaultShaderPostProcessorPlusShaderConverterTool_1.1.unitypackage, download here. There's also a post processor in there that's suppose to automatically convert all shaders to Unlit/Texture. You can delete it if you wish. You should now be in a pretty decent starting place to preview the space in Unity.