In boxing there will be times you are pushed past your limits, boxing is the ultimate workout. Check out your local boxing gym. Watching their trainer's in action can tell you a lot. Do their fighters look sloppy or are you impressed. Most sports clubs have trainers on their staff, but are not famous for boxing.
Some sports clubs offer boxing classes, but most are just for fitness purposes.
If you just want to box for fitness a trainer who works with pro fighters may seem cool, but they probably won't give you the attention as they would to a dedicated fighter. Still could be nice to try their service. If there are no boxing gyms near you, maybe try advertising locally for good trainer, ask other sports trainers who they know and recommend, just don't give up. Your first couple times in the ring you will be sparring with a trainer. The first thing you will notice is that he isn't standing still, he is ducking, bobbing and weaving, your punches just land into thin air.