HST is a relatively easy program to set up, especially if you're doing it "by the book," which you should be since it's your first time through. Just read the FAQs (cannot stress this enough) and some of the articles around the site and you should be able to set up your own cycle. If you still have questions, then post 'em on the board. Once you've got a good grasp on how to set up your program, then simply choose your exercises, plan out your weight progressions, take an SD (9 days minimum), and do it!
IMO, the only reason why you would need a trainer with HST would be if you need to learn the proper form for some exercises. In other words, you'd only need a trainer if you're a total newbie to lifting. It's nice, although not required, to have a spotter when doing HST, but there's no real need for a trainer.