are changing bushes a difficult job? done a lot of stuff on cars but never changed bushes...
Alfa don't sell the bushes separately, you have to by the hole trailing arm that's is faulty, if you take the OE route.
Or follow J5 suggestion and go powerflex route (it's also cheaper).
If you don't have a good hydraulic press (about 20 ton), drilling out
the rubber and then cut the outer metal "tube" of the bushes with
a hacksaw is the best way to go, bee aware that some of the Powerflex bushes need to be cut down by the width of the brackets that they are delivered with (or exclude the bracket's as i did, but i don't now the impact on the life spann of the bushes by doing so, but so far i have not have any trubbel) , use plenty of copper grease when you put the new bushes in place.
And i think you should save the rose joint's if they are OK (no powerflexing there).
Be carefull not to use any "bending" force when you put the arms
back or you may snap the subframe.