travelsafar, don't worry about being able to hear instructions. As said previously, the radiographers talk to you through headphones, so can hear all the instructions,
It does get intermittently noisy and the first time you hear the loud noise you may get a fright.
I have had lots over the years and have always found staff to be very kind. The most important thing is to lie still, which is difficult if you are in pain. The worst thing that happened to me was that I had an itchy nose and couldn't scratch it!
.
I have had full body scans and that takes some time, so I find ways to distract myself. Usually I take myself back to a happy memory or count backwards and forwards to 100 in a foreign language. (I know, I'm a bit odd!
. )
At my last MRI, the radiographers thought I had died, as I was so still. I just wanted to get it over and done with, so I was very determined not to move.
The anticipation is worse than the actual procedure, so don't worry.
Good luck and I hope you get some relief from your pain.