I have had a personal trainer at Goodlife Fitness on Larry Utech Drive since the fall of 2011, which was its grand opening. It is an awesome facility, you may want to check it out.
I would highly recommend using a personal trainer. Your chances of injury are far less with one, not to say you can't tweak something just the same. The classes are ok, but most of the injuries I've heard about occur in classes because the trainer cannot watch 25-30 to ensure they are doing their exercise properly.
The have a head trainer there who usually will talk to potential new clients to see what she/he may be looking for and assign them a personal trainer who will best fit their needs. In my case I wanted to lose some weight, more endurance, and agility. I've been with the same trainer since the place opened in the fall of 2011. I've went from 260 lbs down to 204 lbs, just like losing a small person. I now have energy to burn!!!
So of course I am quite bias when it comes to trainers, but it is sure working for me. I might add I was out for 6 months during that time as I had to have surgery. The Dr.s and VON'S attributed my good recovery time to the 8 months prior my surgery working out.
Good luck, and all the best to you!