Think about the next few years when you buy a radio. Or get a cheap one and buy another later, then you always have a spare.
For a 2.4 Ghz system, it should be the same brand and type, so you can use the same receivers.
Regarding to the mentioned switch - most tx/rx combos come with a switch.
You will probably need a servo extension for the aileron servo. Leave it plugged in the rx, so you don't have to plug it into the rx every time you put the wings on.
Also - the servos come with a wire, in your trainer they should be long enough to reach the rx, exc. the aileron.
The most important thing you will need is an instructor. He can look over the plane, help you build it and teach you to fly.
I am sure you have a club nearby - becoming a member will save you a lot of time and money