Unbolt the axle end of the shock and compress/extend it. You'll know if it's bad. Any oem or aftermarket stabilizer will work. They are all valved 50/50 so they all work the same. Some are built tough, some are built to rust the very next day, and some are built to look pretty. I run a skyjacker one cuz it's cheap and does what others do. I used to run Old Man Emu on my TJ cuz it had a cover over the shock shaft and that protects it from road debris, which would chip it resulting in the seal getting torn and leak starting. Since i don't do alot of highway driving, i have no need for that $$ stabilizer.
HTH