I just completed the install of BMW OE 66mm CABs on a 2000 323i with 82K miles. Here are some suggestions for making the job a little easier:
1) Forget about jacking up the front. Instead, jack up at the jack point behind the one that you want to put a jack stand under. It's fast and safe.
2) Others have indicated that you need a 16mm deep socket. If you don't have one, use a 5/8" spark plug socket. Works great.
3) Don't remove the brace totally. Instead, leave one of the four bolts and reinstalling the brace will be a lot easier. So if you're replacing the driver side CAB, loosen the brace bolt near the passenger side CAB, remove the other three bolts and swivel the brace out of your way. Also, for the bolts near the CABs, there is a spacer washer between the brace and the chassis so be careful not to lose it.
4) Before removing an old CAB, use a Sharpie to mark a reference line so you'll how where to position the new CAB. Remove CAB using a 3-jaw puller borrowed from Autozone.
5) The easiest way to get the new CAB on to the control arms after lubing with Dawn: screw a bolt into chassis hole just below CAB holes. This is the hole normally used to support the brace. Then use a flat pry bar with tip against the bolt head to lever the CAB on to the control arm. Works like a charm. If this is confusing, it will make sense when you're lying on your back looking up at the control arm and trying to bang the CAB on using a mallet.