Dai Davies
Hello Colin, and welcome. Many locos can be EMed just by pulling the wheels. You can buy a special gizmo for this, called a wheel puller! Mine is made by GW Models, and there may be others out there.
For your Alan Gibson wheels, you will need a gear puller, also made by GW Models. You will also need a wheel quarterer. Remember to get spacing washers to go between the wheels and mainframe.
I don’t regard myself as a superfine modeller, just average; and these are jobs that average modellers can easily do. If you get problems when you run the locos, it is generally a quartering week that needs to be done, or making sure the wiper contacts are spaced out to the new gauge. Easily spotted and easily rectified.
So, breathe more brave and get on with it, cheers, Dai Davies