I've been offered an unused P1 exhaust for £100 - is this a good price??

Initially wanted to go for the scoobysport option but this does seem like a good deal - is there much of a difference as far as sound/performance gains go?? Also - I was told that the mount for a P1 exhaust was "slightly different" to the standard one - exactly how hard is it to fit?? - Anyone fancy writing me some instructions down???!!!

Thanks in advance... Kelvin.

 

anyone???