I have done quite a bit of wiring mods to my TTs. Due to the differences in how mine have been constructed, different approaches were needed for each one. My present TT has solid foam block insulation in the outer walls. It does have an enclosed under belly, and a lot of the factory wiring runs inside that. So I have done the same, running wires up thru interior walls from the underbelly. Sometimes I had to come up under a cabinent and then go sideways thru the cabinent cavities to get to the wall that I needed.
In short, without actually seeing your unit... Nobody can say for sure what your best approach will be.... You do need some understanding of how all this stuff works, and the ability to solve the problems that will come up..
FWIW, my only solution to adding a receptacle at the kitchen counter location consisted of using a power strip. It works well and was cheap and easy.