Here is a picture of one I built using a wine cooler I purchased off CL. It will probably hold from 4 to 6 egg boxes easily.
http://i1247.photobucket.com/albums/...cubator002.jpg
Believe me when I say I am not a very handy person and yet had no trouble putting this together after reading the threads on this forum. We have our first clutch cooking right now and everything so far is going well.
Since you have plenty of time, you should give it a try first, as it is much less expensive then one you would purchase.