Can't speak for the pitman arm (never done one), but the upper mount isn't that big a job. If I remember correctly you'll need to remove the rear shock which is just the big bolt down the bottom (22MM possibly) and the three small ones on top (under the parcel shelf - 13MM) then compress the spring to get the old shock mount off. Fit new one and refit the shock.
Full details at:
http://www.bmwe34.net/e34main/mainte...ear_shocks.htm
Stu.