changing runner forks?...piaggio or pm tuning.??

Hi,
I'm looking at changing my origional forks on my runner 172, these are the origional grease filled upside down ones..firstly is this difficult to do? and secondly I was looking at replacing them with some right way up piaggio items or possible pm tunings monster forks..anyone had any experience with these??
Cheers

 

Changing the seals and nylon bushes is a real arse of a job, and if the stantions are pitted just change them!

 

Thanks for that, yeah that's what I heard, was gonna try and get the slighty later model right way up forks, apparently they perform better too...or so i'm told..