Burned an analog port.. how to debug to see what needs replacing?

So, i was there the other day thinking "Boy, it's such a hassle to change my hotend since i have to take out all its cables from the ribbon.. I should get some plugs for fast hotend switching", so i ordered a set of molex plugs and as soon as they arrived i started cutting the thermistor cable so i could attach the plug when *SPARK*... i had forgotten to switch off the power supply. The temperature got stuck at 186°, everything else was working fine. So after researching a bit and posting in the forums, i managed to change the thermistor port for the main hotend to the secondary hotend one and everything is well in the world again.
I have a RAMPS 1.4 board run by an Arduino Mega with the Marlin firmware.
I was wondering though, what needs replacing if i ever want to set up dual extrusion? The RAMPS board, the Arduino Mega or both?
Many thanks for the replies