Replacing the cylinders is just kind of intuitive, you find the bolts and line connections, disconnect them and remove the part.

There are only two things about the hydraulics you need to know that may not be intuitive. First, at the pedal linkage to the master cylinder, there is an eccentric. You need to adjust the eccentric to ensure that there is no pressure applied to the TO bearing whenever the clutch pedal is released. There is an elaborate hydraulic procedure to do this, but you can simply turn the eccentric until you have a little free play at the pedal and you'll be okay.

Secondly is the bleeding procedure that you have already learned something about. In my experience, if you simply bleed it with the two man method and then let it sit overnight, it will probably be okay. If you let it set after bleeding and watch the m/c reservoir, you will see bubbles working their way into the reservoir. Ensure, of course, that the reservoir is topped off after bleeding so that the bubbles don't come up and decrease the level below the clutch supply line.

Now for the part that you will not want to here. I have experienced exactly what you describe. I went through the hydraulics thoroughly only to have the clutch OCCASIONALLY refuse to release. I finally pulled the transmission and found a broken pressure plate finger rattling around inside and occasionally balling up the works, preventing the clutch from releasing.

I wish I could remember more about what some other symptoms were, but that was almost 20 years ago in my first 240D, a '77 with the Factory clutch that had over 250,000 miles. It was just stress that caused it I believe.

Best of luck,