I have to agree with RCKen.

You WILL WANT the trainer.

The glow plane is going to fly about 3 times faster than your Aerobird AND you will be using ailerons which you have not used before.

You will also find that the glow trainer is going to respond MUCH FASTER than the Aerobird.

Next there is the "minor" problems of take off and landing. You are used to hand launching and bellying the plane in - you can not do that with the glow trainer.

A simulator will help, but as RCKen said, talk to your LHS AND also check the AMA web site. It certainly seems that there should be other people in your area that fly glow planes. Even if you need to travel a bit (at least initially ) in order to get used to flying the glow plane it will be worth it in the long run.

As for the Mustang. The MAJORITY of warbirds tend to be a handful to fly, and some are worse than others.

I feel that you will be disillusioned quickly by the Mustang and feel like you are in over your head if try the glow trainer without an instructor.