I have updated my tutorial and plugin for 4.14 with opencv 3.0. There was a small API change which is included in the updates. 
As for the dll problems, your system needs to know where the dll’s are at runtime. In my tutorial I suggest putting the ‘opencv_world300.dll’ file in the binaries folder of your project. This works for play-in-editor, but if you use any other features (such as packaging your game) then you will need to place this file in the same folder as your project’s executable (project.exe) file.
Have fun with your OpenCV / UE4 projects!
-Ginku