shocks are very easy to replace on the w123. the fronts might take 20 minutes a side.. and that's if you're taking your sweet time to do it.. the back maybe 30 minutes a side.

KYB shocks have been good for the w123's i've had.. the first shock change i did was on a 79 240d.. with 475k.. 2 of the shocks had absolutely no resistance! the difference made on the steering was amazing.. the car with bad shocks was scary to drive on the highway and would want to jump lanes if you hit any bump or imperfection in the road! new shocks fixed that