Agreed it can be intimidating if you have no experience.
If it's a little out of your league, set it aside, build a few from scratch, and when you go to repair it, you'll be wondering what you were so worried about
Alot of the conversations here make it seem much more complex than it really is. And as far as a diode replacement, two wires and your finished assuming it's just the diode that's shot.
With all the "pre-wired" and "preset" drivers, these things are damn near finished when they are delivered.
Plug and burn host, pre-wired module from DTR, your looking at a 5 minute build. Soldering iron, shrink wrap, Allen key, done. Big boy Lego set
I would grab a 501B from Mrcrouse ($20) a pre-wired m140 with x drive 1.7w ($100) solder 2 wires, and you have a close to 2w pocket 445nm for $120, and the satisfaction of building your first laser.