I did hours of research before I popped open my first stampede; my advice would be to dip into the great wealth of nerf videos and internals pics here and on the web, to familiarize yourself with the internals of the blaster(s) you want to repair. Watch mod tutorials, use the search feature on the haven, etc. if you have the time and tools for the job you should be good.
Opening any of my Nerf guns makes me really nervous. I'm always afraid I'll lose something or put something back wrong.