Well, absent a subscription to a paid legal search engine such as Westlaw, BNA, or Lexis, have you tried any searches for actual case decisions under FindLaw? I'm not sure anything precise will come up that way, though.
Otherwise, you can also do a search of the Federal Courts (in the State of Texas).
Believe me, given what little you have stated here, and as complex as ADA and employment cases are, I would definitely consult a good employment attorney.
In reference to being a public employee such as you mentioned, are you under a collective bargaining agreement with a Labor Union? If so, contact your International Representative or Local Union President, who can help you obtain legal assistance from your Union headquarters.
Otherwise, trying to interpret any court decisions that you do find may prove to be quite complex. ADA and employment/labor situations are very complicated.
EDIT: Of course, if you are really intent on trying to understand or read up on the ADA, you can visit the Department of Justice's website at http://www.usdoj.gov/crt/ada/
Another good site for general information which may be more understandable than what the individual titles of the ADA under the Code of Federal Regulations may be for you, is the "Job Accommodation Network" at http://www.jan.wvu.edu/
I hope this helps. Again, though, this is all very complex, and I would not suggest you attempting to make any decisions or taking any actions whatsoever on your own without consulting an attorney.