Caveat: I am a personal trainer. So what follows may be biased! 
A good personal trainer, one with plenty of experience, will be able to interpret your goals and create/adapt your training to help you meet them. They should be able to find a way of working out that suits you, and that you enjoy. Weights could be part of that for you, but you'd need an assessment first to be sure.
You should look for someone who is REPS registered and, ideally, has several years of experience. A BSc in Sports Science or similar is a good sign, too. And there's good old gut feeling - training sessions are much more fun if you like the trainer!
It's important to get technique locked down with weight training, as it can quickly become ineffective if it's not done properly and can risk injury.
You mention diet advice. A personal trainer will generally not be able to give nutritional or dietary advice, beyond the 'here are some general healthy eating guidelines that apply to the average adult population' stuff. For more tailored advice, you would need a dietician or a nutritionist.
(The title of dietician is protected by law, but nutritionist isn't. So, theoretically, anyone can sell their services as a nutritionist. Some nutritionists are good, and well-qualified, and some aren't. However, there is a regulatory body that will list reputable nutritionists; the Association for Nutrition.)