Assignment Despite Objection?

Hi everyone. Just found out I am going to be floated in another clinic this week, where they do a lot of procedures. I've floated in this area a few times before, but the last time I was there was more than a year ago. I was just informed that the joint commission surveyor is here in our hospital, and this particular area is one of the hotspots (they scrutinize this area more than others). I am extremely terrified and nervous of going there now as I haven't been there in a long time. I don't want to be blamed for anything and be fired. I feel that the gap is way too long from the last time i've floated there and i didn't receive any training or in service about the changes that happened in that area while I was away i.e., new iv pumps, new protocols, new procedures etc.

Also, I am not familiar where everything is in that clinic (like supplies). I am also afraid that i may not be able to answer some jhaico questions as i don't normally work in that area.

I am thinking of writing a letter to my manager and let her sign stating that I am not comfortable floating in that area. what do you think?. is this justified?