This manual will probably have most of what you need:
http://byoguitar.com/Images/products...structions.pdf
There are really 2 important things in the assembly that will greatly affect the playability. One would be making sure the neck is glued properly so it has the correct angle. Normally that's taken care of if it's milled correctly, but you never know with a lower end kit so it wouldn't hurt to double check. That manual above outlines how to check for the correct centering and angle of the neck. I'd also look at other tutorials and/or videos of people assembling set neck guitars; whether they're SGs or not the process will be pretty similar.
The other big thing is going to be the setup, and it can sometimes be tough with a cheaper kit, but with enough patience it can work. Again, the manual above outlines that but also look at other info. Basically you'll have to install bridge and the nut, maybe even filing the latter down to get the action low enough. You might have to adjust the truss rod if there's any bow in the neck, and the frets might need leveling (though hopefully not). Here's a rough guide on setting up a Les Paul, and most of it should apply to an SG:
http://diystrat.blogspot.de/2012/09/...aul-style.html
Other than those things though, it's mostly just aesthetics. Finishing can be tough and frustrating but there isn't much that isn't reversible if it comes to that. The translucent green finish won't really look the same as that picture though because the SG is mahogany while your kit looks like Paulownia or Ash. It'd probably look more like this:
http://www.carvinguitars.com/guitarg...ll/pb4-tpg.jpg
Probably the most important thing regardless of which part of assembly you're doing is to take your time. Break it down into a bunch of small steps and really think about each process before you do it.