Hi Roy
If putting in the engine is all that you don’t understand then you should have no problems building this model.
Does your plan show the position of the engine?
If so all you have to do is keep the engine shaft in line with the prop shaft to eliminate any shakes. All the other ancillary bits such as battery, receiver etc can be placed within the hull to suit ballast and trim i.e. wherever they fit best to suit the look of the model when in water.
Bite the bullet my friend and enjoy the build.
If you come across a problem there are lots of us on this site that are only to willing to help with advice based upon practical knowledge.
All the best for the build
Paul