not difficult at all. its in the manual. be very careful not to lose the 2 ball bearings that are in the lpr adjuster assembly. There is a big one that presses on the dime shim and there is a smaller one further inside the adjuster that pushes on the bigger one. also if you remove the shrader valve from the inside of the lpr housing (you should since you're already in there) it has an oring on it. this oring is NOT in the manual. It is a standard (non-metric) oring, can't remember the size off the top of my head, I have it written down at home if you really need to know....but I want to say its a 006...
also there is a black rubber seal on the shrader valves, it is not replaceable, do not try to remove it or mess with it, just clean it and inspect it. make sure when you replace the LPR piston oring be sure to fill the oring groove with dow 55 before putting the oring on. this grease will act like a "reservoir" of sorts to continuously lube that oring. they make the grooves with a little extra room just for this purpose.
If you decide to further tear it down to replace all the orings since you'll already be 1/2 there with having the frame removed you should know that there are several other orings that are not listed in the manual including:
ASA to grip frame (wrong size listed)
3 orings inside of asa
2 orings HPR insert (part that HPR screws onto and the sharader screws into)
maybe one more, again, have it written down at home
i contacted the guy that wrote the manual about making a post with all the missing oring sizes but....haven't really followed up with him on it.