No need to solder anything. You can disconnect all wires from current transmitter & connect them to new transmitter. I'm not sure about the wires for ON/OFF button though. I changed from FM to 2.4GHz & the ON/OFF wires are soldered on the FM transmitter board. The 2.4GHz 2013 rev4 transmitter I have here use connectors for everything (see pic below). Just plug & play. Basically just need to plug in all the connectors (female connectors) to the appropriate socket (male connectors). I don't know whether the old version of 2.4GHz transmitter also use the same approach. I have extra female connector with the appropriate size. I just wired the ON/OFF switch wires to it & secured it with electrical tape. You can see in the picture in my previous post. I can do better if I have crimping tool.

On the left is 2.4GHz 2013 rev4 transmitter. On the riight is FM transmitter.


Do you know how to bind the transmitter with the receiver? If you don't bind them, you won't be able to use them. I don't know for sure whether you can use current transmitter with ver 2 receiver. If it doesn't want to bind then you'll need new transmitter.