dot 5 is silicone. as your buddy said very difficult to get a swap without replacing everything.
silicone is the preferred fluid for classic cars that sit for long periods. the reason stored cars like it is because it does not attract water like dot 3,4 and 5.1. the normal fluid would get enough water in the system that pistons would rust and pit the cylinder walls (none disk), if left long enough without use.
I don't know why but I have never seen it used on race cars. beyond the water issue it must not have any positives better than a good dot 3,4,5.1.
in a nut shell, not worth it for a dd or even a once a month track car.