By "oil catch can" you are referring to one installed in the PCV system, correct? Depending on the PCV valve location, it can either be a very difficult or very easy install.
Here is an example of a PCV catch can setup on a Pathfinder. Scroll up a few posts to see the parts required. Perhaps this will help you get an idea of what you need if you wish to install one.
As for the magnetic drain plug, I know
Courtesy Parts sells one, but it's fairly expensive. If you have any dead computer hard drives lying around, you can disassemble them and put the magnets inside on the exterior of your oil filter to hold ferrous material.
