Hi
to the forum.
I just read about someone using a stress ball and music a couple of days ago on here. If you think it will help then take it with you.
You shouldn't have any pain while treatment is being done, if you do feel anything let them know and they can give you more of the numbing stuff.
I have had a few rct's all pain free, they aren't to be feared. I understand your anxiety, but you will be amazed at how easy they are to get done. You will feel nothing, the worst thing about a rct is that they are boring. There is very little drilling and the work on the tooth once access is gained the rct is done with little hand files. It will be over before you know it.