This isnt mine, just need a picture for an example and easy description.

http://www.classiczcars.com/photopost/showphoto.php?photo=23386&cat=500&ppuser=11415

That filter there on top of the engine were the PCV valve is, what is that exactly called? Also, is there any advantage to replace the peice of tube that goes into the air box for the air intake with a filter like that?

Also, if you do replace that piece of piping with a filter, do you need to plug the hole in the air box?

Yes you have to block up the hole in the air filter box, or you will be sucking unfiltered air into the engine.

http://www.classiczcars.com/forums/showthread.php?t=5348

That filter there on top of the engine were the PCV valve is, what is that exactly called? Also, is there any advantage to replace the peice of tube that goes into the air box for the air intake with a filter like that?

Not if you still have the stock air box for the tube to connect to. In fact I've heard of several drawbacks to those little filters, including oily mist in the engine compartment, oil fumes in the cockpit, etc.