Then you might know the E70 bushes are an 'upgrade' on the E39. A true 'OE BMW hack'.
Definitely do both sides at the same time.
Id use OE/OEM, you get 60-100k, seems pretty good
Ive never done a bush replacement in-situ. Arm out, press out/in, reinstall. There are portable hand-held pneumatic presses that make it super easy.
Id probably do the whole arm at 100k
GL