Very easy Chris
Open the back of the TX
There is a flat spring against a ratchet on the back of one of the controls which can be unscrewed and moved to another one (silver piece at the top of the photo between the switches) and a spiral spring, usually on the other direction which is attached to a small plastic piece on a fixed pillar at one end and a protrusion on the other (not very clearly seen under the yellow and black wire in the right hand bottom corner) which gives self centering, and can be unscrewed and moved to the other direction.
If you want both to be the same type, I am sure your local dealer will supply a new spring, plastic piece and screw.
I have completely changed my Tx around and changed one of the controls to a slide pot and the other to a wheel.