i don't think you need a trainer, at least not for more than a couple of sessions. programs like starting strength and stronglifts are great heavy lifting programs that are progressive, starting at very low weight so you can begin by focusing on form. if you need a trainer at all, it would be to have someone to show you proper form and check your form, then you can follow a program on your own. for that, the advice you can get at a crossfit gym should be just fine. see if they will let you have a couple of trial sessions where you can work with someone who knows what they're doing.
also consider some of the body weight programs like simplefit, primal blueprint fitness, convict conditioning, etc...it may not seem like you're doing a lot of lifting heavy things at first, but i work harder doing those programs than i ever did under the bar.