It will mentally drain you.
They will hover over you during your typing test and diction test, so be prepared to have somebody over your shoulder watching you during your test.
Practice repeating everything on the radio
To breath. Make sure you practice some with online typing test. I typed 59 wpm was hired with no issue. Also, practice repeating what others say rather this be the radio, YouTube videos, etc. Lastly, breath. I was a nervous wreck going into the test/interview. When all is said and done it isn't as bad as you think it will be.
They test typing speed as well as voice to text accuracy, so make sure to prepare those. Outside that, the interview is pretty easy.