I've used a trainer in the past and found it beneficial. I was very sedentary and was just starting to exercise and wanted to work effectively without hurting myself! I bought a ten session training program and was able to choose the trainer. I think that's key, you need to talk to potential trainers and see if they meet your expectations. The woman I worked with was sweet and pushed me as much as she thought I could handle. Yes you can get the info on your own, but for me it was easier to have someone say "this is what you can do and this is how you should move and how often." And the ten sessions were spread over six weeks so I was developing the workout habit, which was great.
Now I'm starting out again (sigh), but I know what to do. Another thing to consider is that if you just want to know how to use gym equipment, someone there will show you at no charge.