At that price, i would buy those arms and not bother replacing parts on the arms themselves, as said, ive not done the bushes but the ball joints was something i didnt enjoy other than the cost saving.
When you lower your subframe to remove the rear bolts on the arms make sure you put pressure on the subframe near the bolt with a jack, if you dont you risk the captive nut breaking free from its mounting and if that happens you have to lift the carpet in the front footwell and make a hole in the floor to get access to it with a socket.
Sounds worse than it is, there is an area clearly designed with it needing access in mind should the nut break free, strips of metal which you cut away rather than solid floor pan, just a pain you dont need and a mistake i made on my previous mk3!
If you lower only one side of the subframe, do one arm the bolt back up and do the other side, you should not need to align the subframe, you will still need to have your tracking done though.
Not a pic taken by me but this is what i mean about the strips to gain access to the captive nut, its not as violent as it sounds