Yes, get an instructor.

Your flight experience will help a great deal in understanding the mechanics of how your models fly, but it will help very little in actually controlling the plane. I've known USAF fighter pilots who had been flying for 15 years who had to relearn flight for R/C. It is very different.

Good idea on not using the the Showtime for a trainer.

If you want expandability and control, I'd get the JR 9303 air or heli. The 10x is a fine radio, but in a few years, when you are ready for 40% IMAC type planes etc., they will have released something new and better. The 9303 is a lot less expensive and has most of the functions of the 10x. It is the radio I chose for my return to the sport and hobby of R/C flight and is what I would recommend based on what you've said.

I would get JR DS821 servos run off of a 6v rx pack for your Showtime, and some analog servos for your trainer.