[ENINTY]

I've not removed the exhaust on my 325i yet (I might be doing it this weekend to check my drive shaft splines), but I've done sveral other 3-series and they are all pretty much the same. A few pointers:

You'll find the nuts are not rusted too bad. BMW uses good metals for the nuts. But get new OEM nuts for the flange where the exhaust connects to the mainfold.

The exhaust is long and heavy. Get the car level and as high up as possible.

Make sure downstream O2 sensor is not located in the part of the exhaust you are removing (i.e. past the manifold flange break). If it is make sure you UNPLUG IT FIRST before removing the nuts and hangers.

Use rolling floor jack to ease it down.

Get a set of exhaust hanger pliers (Leslie tools makes a nice set) to remove the rubber hangers.

Get a new gasket(s).

Let some penetrating oil soak into the mounting bolts for awhile. If you have access to an impact wrench (electric or air), I suggest using it because it makes the job of removing the nuts much easier.

Remove the center mount that is bolted to the transmission rear mount.

Unbolt it at the flange break. Let it hang. Center-balance the exhaust on the jack and pre-load it a bit (i.e. jack the exhaust up an inch or two. Remove the hangers once you have the exhaust center-balanced on the jack. Use some type of strap to hold the exhaust to the jack. Remove the hangers from the muffler (first) back towards the center of the car. Ease the exhaust down.

It's best to have a helper.