RE: Good First Warbird?
Although not scale, the Great Planes P-51 is a great kit to begin with. It also is a great flyer that you will really enjoy after flying the easy sport.
Apart that it is a .40 size plane, I suggest starting with it before trying a TopFlight or Pica kit.
If the GP P-51 just won't cut it, then look at the kits by Skyshark RC. These laser cut kits don't require a lot of guesswork and finish as a nice warbird that you can glass, paint, and install retracts.
Scott