I don't have much for plumbing skills either, and have built my own.
I used a U-Tube overflow like this:
http://www.aquacorals.com/ShopOverflows.htm or this:
http://www.lifereef.com/siphon.html to avoid having to do any drilling.
In my overflow, I experimented with a few different stand-pipes, from a short Durso (didn't work as well as it might have - I used straight 1 inch pipe and should have used bigger), and would up with one of these:
http://home.everestkc.net/jrobertson57268/HGB/HGB_construction.html
I siliconed glass baffles into a 30 gallong glass tank, but sectioning the thing is optional - if you just want somewhere to put the skimmer and other filtration stuff, don't worry about it. People also simply nest containers (like put a rubber-made tub into the sump) to make compartments, like for a refugium.
I used PVC pipe to build the drain from the overflow to my sump/fuge, because I wanted to split flow unevenly between my refugium and skimmer sections. A far simpler approach would be to just use clear vinyl hose for that.
My return to the tank, I used clear vinyl hose. I did put a ball valve in there so that I can dial back flow if I have to.
I'm using a Via Aqua 3600 pump for the return. Another popular choice would be a Mag-Drive 9 or 12 (I think). Basically, you want it to push somewhere around 300 to 500 gallons per hour with 4 feet of head or so. That leaves the water with some dwell time in the sump, and is under the theoretical capacity of the overflow.
As far as floods go, they can happen 2 ways: the return can fail and the tank can overflow, or the pump can fail and the sump can overflow.
The first of these is the one that has me worried, but basically what I've planned is I keep the water level in the return section of my sump low enough that the pump will run dry before the tank overflows. I have a feeling that I may wind up having to top off way to frequently that way, and it might not be workable for a sump without baffles. You could also do something with float switches, but I'm worse with wiring than I am with plumbing
Note that the most likely overflow failure isn't loss of syphon in the HOB overflow: it's a critter jambing the thing!
As far as the pump failing and overflowing the sump, that's just a matter of math: make sure that you have enough extra room in the sump to hold all the water held in the tank over _both_ the overflow box _and_ the return nozzle. If the pump fails, the return plumbing turns into a siphon that sucks water out of the tank until it sucks air! Keep the return nozzle close to the surface to help on that.
Well, that's quite a lot of writing, but it's pretty much what I've digested from reading this forum for the last six months.
