soak the bolts beforehand with plusgas and clean the threads protruding through the ball joint with a wire brush then clean the dirt out of the allen key headed bolts holding the balljoint to the arm , also cover the threads protruding with grease so it makes it easier to undo , you will need a balljoint splitter or you could just shock it with a big hammer, whole job should take you no longer than 20 minutes per side and its very simple to do you dont need to use a garage anyone could do it
you just tighten them up into the top arm its the lower ones what need pressing in , you will need a big ring spanner to undo the nut on the bottom of ball joint think it may be 29mm as not done one for a few months
the upper wishbone replacement is more complicated as you need welding gear to refit the bushes and the quality of most replacement bushes is terrible so they dont last very long
I replaced both my upper ball joints this week, had to cut the head off one of the bolts as it rounded but apart from that it was easy. I bought mine from brickwerks, not cheap but the quality seems very good and they came with new bolts.