What to expect from PIP 'review' assessment?

I have a couple of questions relating to PIP and thought I would keep it to this one thread, firstly what is the difference between the PIP assessment for a review and the original assessment? Or will they just be identical?

Also, I sent back my review forms at the start of October and have heard absolutely nothing since, PIP has just been being paid in as normal. I presume if the award was just going to be renewed then I would have heard from the DWP by now, so its more likely I will be getting called for another assessment at some point? Or have I got that wrong.

I had a text today stating 'Thanks for sending us your how your disability affects you form, we may need you to attend a consultation, we'll contact you again if we do'.
So months and months later it seems they have got round to looking at my review and looks like I will more than likely have to attend a face 2 face, this has now filled me with dread!
I want to prepare myself so I have the best possible chance of keeping my award which is just the standard care.
Do you have any guides specifically for the assessment?

I had the assessment this week and its triggered the worst anxiety, as I just do not know what to expect, I am hearing so many horror stories and someone I know has been talking about preparing myself for mandatory reconsideration and tribunal as most mental health fail the PIP test.

I wanted to ask, the assessor said to me at the end - ''i shouldnt really say this but you have nothing to worry about'', (in regards to my claim) obviously that should have put my mind at ease, but do they just say this to everyone?!
Also how long on average at the moment to wait to hear about a decision?
thanks