The mod isn't as important on a diesel as it is on gassers, but if you're going to mess with the intake piping it's required. The thing you need to be aware of is that these trucks put out a TON of blow by, sitting at idle. As far as a puddle, it's not that bad but you will get drips if you leave it vented to atmo.
If you do it, route it to the exhaust, otherwise you'll smell oil vapor in the cab. Only costs the price of welding!
Here's the link to my post on my updated version. There is just a slight vacuum with this setup, and by slight I mean SLIGHT! There's is no way in hell you can pressurize your crank case with this setup:
http://powerstrokearmy.com/forums/showthread.php?t=64954&page=12
If you have ANY questions feel free to PM me. I've had this mod for half a year now, zero issues.