Most Firmware updates do one of two things:
1) Fix bugs - Yes
2) improve performance. Depends if minor performance boost, probably not,as you would not detect a real performance increase in day-to-day usage. If a good performance boost, then user call.
NOTE: some times manuf do NOT state all the changes which would indicate probably a good Idea.
Absolutely Yes, if there is a bug that will cause you a problem, or if you are experinencing problems. ie Crucial M4's had a bug that would "kill your SD when it hit 5000 Hrs. Intel had a bug that would cause the SSD to suddenly drop to 8 mb size - ouch.
For deteriming Fireware installed, yes magician will work fine. Personnaly I like to run AS SSD as it will indiate:
.. Make model
.. Fireware installed
.. Driver used (ie you DO NOT want to see "ide = BAD"
.. Partion alignment - want to see "OK"
DO NOT need to run the benchmark, just open the program and look at the upper left.