These pictures outline the simple check on my 60A TCM alternator.  The entire back of the alternator comes off without removing the main housing from the IO-550.  I suspect the 100A units are similar.   The stator can get stuck but it will come with the back half of the shell as you see in the first photo.   It must come out together because those three stator windings are attached to the diode pack.  The replacement diode pack is pretty straightforward.  Diodes come in varying capacity so higher amperage is generally better.  That stud is pressed out of the old pack and pressed back into the new diode pack.  That's the output bolt for the alternator.  At $12 per pack, it may not be aviation quality but it works better than what I had and at that price you can easily afford to have a replacement on the shelf.  The rotor and commutator rings get a quick polish but it is so clean and there's hardly any brush dust after almost 700 hours.  If you need to inspect the coupling then the front hald of the housing would need to be removed but that's a bigger project.