Is it safe to try different firmwares on EV3? I have prepared a SD card to run Lejos on EV3, as said on Lejos Sourceforge page and I'm about to test it. What worries me - will I still be able to go back to original Firmware if something goes wrong or I'd like to go back to this original Lego visual building software? 
Will removing SD card be sufficient?

Thanks for any information.
I tried Lejos and removing the SD card and rebooting was enough to go back to original firmware.