alot easier on a ramp, dont need a special tool either. IIRC the big nut in the middle at the top is 22mm, you can get to it with a long ratchet with flexible head

best to buy the whole arm as said above. You are also better off buying the back bush complete, trying to get the old ones out & get the new ones on are a nightmare if you havent got a press.

done both arms on my Mrs beemer (e36 compact) last weekend.

NB: When you put the new bushes on the arms, remember they have to be slightly angled, so have some tipex ready to mark where you have to push them on. Use the old ones as a guide. Another tip is to wire brush the paint of the tips of the new arms to make it easier to get the new bush on (you'll need a bit of grease too)

i bought both arms from euro car parts and where cheaper than camberley autofactors.

HTH