DIY tensioner assembly replacement on a bmw e36 1996 328i. This is a relatively simple and quick job, however it's important to have the proper tools for the replacement, and to ensure that all the bad pulleys are identified and replaced.
The quickest way to ensure this job goes quickly is to have the fan clutch removal tool on hand, this gives you the room to ensure a quick replacement of the tensioner. 
The first thing to do in order to replace the tensioner is to remove the cruise control, airbox, and alternator air duct. 
Afterwards if you have the fan clutch tool, proceed to remove the fan clutch, remember that the clutch is left hand thread.
The hydraulic tensioner assembly only has two bolts holding it to the block. One on the top, and one relatively difficult bolt on the bottom, which is hidden by the pulley.
After removal of the assembly, installation is simply the reversal of removal.
At this point you should have a new tensioner assembly and the annoying noise coming from the serpentine assembly is gone.
Other associated parts to replace during this job are the two drive belts and the ac tensioner assembly.