<p>Building a 3-D printer is obviously a huge undertaking.</p>

<p>Does anyone know of any reasonably cheap guides to build my own 3-D printer?</p>

If you just want to build your own, get a kit.  There are several out there.  Most kits take from 1-5 days to complete depending on the kit.
If you want to design your own is quite a different story.  The effort is totally dependent on how much you want to do yourself.  My guess is the statement that you don't know the amount of effort indicates that you are probably not ready to design your own.