I just did that job on my e30 a few weeks ago.  It uses the same bearing as
your e36.  You can do it on a Saturday if you have all the parts and tools
ready to go.
You will need to have a threaded type puller to extract the bearing from its
housing and to install the new one.  I tried to use a slide hammer puller
from my local tool rental shop but I couldn't budge the bearing with it in
spite of some pretty violent efforts.  The bearing pullers are available
from Bavarian Autosport for $275 but fortunately I have a metal lathe and
could make one up for the job although it took me a whole day to finish it.
You will also need a pretty robust set of circlip pliers to remove the
circlip that retains the bearing.  In addition to the new bearing you will
need a new locking ring for the axle nut as it is not possible to remove the
old one without destroying it.  An alternate approach is to remove the
entire trailing arm and take it to your local machine shop to have them
replace the bearing.  The downside being that you have to remove the brake
line and parking brake cable that are attached to the trailing arm.  Or you
can take it in and have it done.  They will charge you 2.5 to 3 hours labor.
The bearing costs $30 on Ebay, $50 from Bavarian, and probably $85 from BMW.
I hope this helps - Good Luck
Jack

Believe it or not, I used a hammer to smack the middle of the hub and it
popped the bearing forward! Nice ;)

Nick