For me it looks necessery to replace the rubber bushes, those also has impact on your ride hight
yes remove the roll pin for renew the absorber.
I never has rebuild the shocks myself , but I know into that the past shock rebuilders from the USA used wrong rubber material internals , they dissolve in oil.
internal parts from Ariston and Koni are not interchangeable
my experiance is that Koni's shocks build into The Netherlands has a locknut on top of the piston, while US build Koni shocks use a roll pin.
The rubber bushes from Ariston and Koni are the same.
Simon