The first 2 salt water fish I had were a Huma Trigger, and an Achilles Tang. When we bought our 1st house the guy didn't want to move the 125 gallon tank, so I took the tank with the house, the Tang had been in for 2+ years when I got him. Being a beginner, I did my best to kill these 2 fish, had the ph drop to 7.3, nitrates went sky high, didn't have a protein skimmer for 6 months, too little water flow...You name it I goofed it up....The 2 fish lived through it, I had both for about 5 years in addition to the 2 years with the previous owner.
Guess what I'm saying is, yes they have the reputation for being difficult to keep, but once "established", they are very hardy IMO. Find one that is eating well, and somewhat fat and hope for the best. Good water quality, lots of water movement, good protein skimming, and greens in their balanced diet. Once they are settled in your in good shape. I will tell you, this is easily my favorite fish I have owned, but it is also by far the most aggressive fish I have ever kept (this includes a list of Triggers, Puffers, Wrasses, Angels, and other Tangs). Be advised, once established these guys will be brutal to any new additions.