The new arms come with the bushings installed, so if you want to DIY that would be the way to go. The bushings can also be bought seperately, but then you would need to pay a shop to press them in the arms for you with a shop press.
And what I mean by on her wheels to tighten is that the bolt through the bushing tightens everything down in place, and if you tighten that with the X5 off the ground and the wheels sagging down it will hold the bushing to that position... and when you lower her back onto the ground and compress the suspension to the normal ride level the bushings will be twisted and will wear/tear abnormally fast. Basically you just want the suspension at the normal ride height when you tighten the bolts that go through the bushings.
There are likely to be some DIY writeups on this site somewhere, just search around and you should find something.
