RE: P 51 ARF or RTF?
Well the PTS was designed as a first model sort of deal and I've seen one of them being demonstrated by a local LHS at a show. I've not talked to anyone who's actually bought that model for a first plane.
They claim it's pretty easy to learn on, but my suggestion would be that you start with something a little more typical for a trainer. That being a high wing tricycle gear RTF. They will be more stable, easier to fly and the takeoff/landing/ground handling will be easier with a tricycle gear.
As for the included radio equipment, that probably won't be a lot of use down the road for more complex models but it will get you going without a lot of expense. I will suggest that it's going to be really difficult for you to figure out which area/type of models/flying you'll decide to pursue after the trainer so buying radio equipment right now that costs more up front may not be the wisest thing to do. I personally upgraded all the radio stuff in my first trainer way beyond what it needed since I had an idea where I wanted to go after flying the trainer and being around other pilots and various equipment setups. So I feel that I skipped the intermediate radio stuff/expense and now that I'm flying IMAC type models with gas engines, the radio will handle those models and even the small electric heli I decided to try.
The other thing is that there is always the chance you might decide you want to go to helicopters, or even that you don't care for the hobby. Getting in for a more limited initial expense with an easy to fly model, to see if you like it, would be my suggestion... [8D]