Control external MIDI synth with Logic Pro X

I purchaced Logic Pro X to use it as a MIDI-sequencer for my external stagepiano: the Roland RD-700sx including two expansion boards (SRX-04 and SRX-10). I want to make records to create my own music. Before I record it as audio I want to record it as MIDI, because in that form it's easier to make adjustments.

The RD-700sx is GM-compatible, though the better quality sounds are stored in certain banks, which one can select bij entering a specific number to the MIDI control assignments MSB and LSB. For example: to select the Superior Grand Piano, MSB = 87, LSB = 64 and PC (program change) = 1. To select the 60's E. Piano 2, MSB = 87, LSB = 65 and PC = 5. To select the first tone wheel organ MSB = 112, LSB = 0 and PC = 1. To select the SX Rock Kit (drums) MSB = 86, LSB = 72 and PC = 2. And to select the staccato cello on my expansion board MSB = 93, LSB = 3 and PC = 79.

I spent a lot of time searching and asking on the internet how to select the desired sounds, but I don't know how to do it. So far I know you have to create a multitimbral MIDI environment and on each of the 16 channels you can assign a bank and enter the values of MSB and LSB. I found this article: Logic Pro/Express 9: Defining Custom Bank Messages - Apple Support

I understand a part of it, though I have too little experience with Logic Pro X to get the job done. Can someone please explain it to me from the beginning to the end? You would help me a lot!!! 🙂