universal joint replacement is fairly straightforward but on the alfa the yokes are not flat and care must be used to drive the old cups out and the new cups in absolutely straight. if they go in ****ed they might raise a burr. If you find, when finishing up, that you don't have room to put in the second circlip, chances are one or more needles fell into the bottom of the cup.
I use small hand press, but a vise can work just as well.
I bought joints from Difatta, and they fit perfectly.