I upgraded my 2010 RV12 last year and to do it right and Van's behind you, only one way. I worked with Van's before and during and I can tell you that the wiring harnesses have to be replaced. Van's told me they had problems with the conversion harness. They recommended all harnesses replaced except the engine and trim. You will also get 3 new pre-cut front panels.
****I got great help from Tony - here above. Tony had some very helpful information.
You will also take everything out of the avionics bay "everything", so basically just starting over. You want just be referring to one set of plans, you'll be bouncing around to several year versions for the correct info.
Was it worth it? Hell Yes It's incredible!
Does it have side effects? Hell Yes, back aces, cuts, eye strain, nerve strain, gut pain from bending over the side and others.
See my blog below for more info.