I decided to replace the whole orifice instead of just the 'spark plug'. In doing so it became apparent that the screws would not come off easily and so I purchased a couple of those to make sure I had enough just in case. Good thing, 2 were messed up taking them out.
It was also pretty dirty after 13 years of cooking so I took the time to clean up most of the bits.
It was a difficult thing to do and took me a while to get thru all the screws in correct order to remove the part and replace.
I would say it was a difficulty of 8 out of 10 for someone who does not do this often and doesn't have all the star screw drivers etc.