Possible, however there's only so much a diffuser can do.
I think installing one is a good call to get an idea for how much light they'll really bring in. It's really hard to tell in the store where you see the demo because the entire store is illuminated as well.
Framing up a skylight isn't terribly difficult, basically build a box from the ceiling to the roof, cut out the joists inside the box, and drywall up the interior. Like with the solar tube though the key is going to get a water tight fit on the roof
Pick up one of those home depot books (or just browse through one in the store or go to the library), it's not terribly difficult in the grand scheme of things. However if you are unsure, maybe poking holes in the roof should be left for the professionals