It's not difficult at all.
We have detailed pictures of how each of us installed the beta units. I won't post them yet until Eli is ready to go, but all we had to do was make a bracket to hold the two emitter boards under the playfield. We used flat aluminum bar from Home Depot and there were existing mounting points under the playfield that made it very easy. Pictures were posted very early in this thread.
With the cradle/bracket bult, it was simply a matter of running the fiber optic cable around the ramps and into the existing holes in the playfield (luckily both pro and LE pfs are the same) and the cabled plug into the two emitters. You will have to probably drill the ramps to zip-tie the cables to them, or use some sort of DS tape, but I was lazy and ordered LE ramps from PBL.
A master board gets inserted into the head cabinet that interupts one of the ribbon cables and reads signals from the game. It is wired down to the two emitter boards under th eplayfield. Power is from the aux supply for the emitters and in the back box for the main board.
I would imagine Eli might package a kit or detailed instructions once the time comes so you won't have to build connectors and brackets like we did
It's a thing of beauty for sure!