The tutorials aren't that hard to follow. Theres a few of them on Avsim. When it comes to the Level D 767, the main attraction is the realism of the systems. If you're not using them for whatever reason you've really just wasted $40.
Trust me, I hate manuals and reading, but the tutorials are really easy to go through. They are a .pdf file if memory serves me correctly, they have pictures and it walks you through the whole flight from flight planning, FMS set up, prestart, all the way to shut down at the destination. After you learn one FMS, they're all basically the same too, so you can hop from the Level D, to PMDG, to iFly, to PSS and so on.
Stick and rudder/steamgaugers will say its not really flying, but it feels great sometimes to enter all that information and have everything pop up for you, and for it to be right! Its satisfying to look at the route page and see everything trucking along nicely, and to know you programmed it to do what its doing and there are no snags in it.
The tutorial is free, and only takes a couple hours to do (if you use time compression). What have ya got to lose?