For what it's worth I recently did the CRI course, and passed the skill test. Whilst not an identical skill test to the one for FI(R), from what I understand the length and standards are broadly similar.
I was having to fly, from the right hand seat, to similar standards to those I had to display during my CPL (not PPL) skill test, whilst talking about it for about half the time, or picking up somebody else's errors the other half.
I loved every minute of it, and am really enjoying the instruction I'm doing - but as a CPL with 4-figure hours, I was heavily challenged. I really can't imagine meeting those standards when I had a PPL and a few hundred hours.
Which is not to put you off - very best of luck, just be realistic about how far you almost certainly have to go.
G