I found the instructions on an RC thread, and I found it fairly easy to build, even with out limited tool selection.
Got all the stuff at home depot and spend about $10-15 on the parts.
I already had an MJ pump around, so if you have to buy one, that would add to the cost.
I'll try to find the thread...
Found it, but unfortunately the creator has moved on, and the pics are no longer available.
But it's a huge thread, and maybe someone else has posted pics to make up for the missing ones!
http://reefcentral.com/forums/showthread.php?t=1288082
Also, I made another one for my smaller tank (about 75G inc. sump) and for that I just used a little reactor like a phosphate one, without a recirc pump, filled in a little sulfur and media for the bacteria to colonize, followed the instructions for getting it started, and it works fine!
No building needed!