stock suspension overhaul opinions

i have noticed that my wagon is riding a bit rough. over sharp bumps or speed bumps, the suspension is very hard. i noticed a while ago that the right (pass) side hydraulic shock is leaking. it is caked with dirt and fluid. i was going to replace that shock. while i was at it, i was going to replace the gas spheres. the spheres are only $200 so i figured i'd just replace them because of the harsh/ridged ride in the rear. would bad nitrogen spheres cause the harsh ride.

anyone have the same problems?

is my course of action reasonable?

and with 108000 miles i am also going to replace the front shocks (original)

any opinions or input?