Digital BW, The Print

I am a new member of the forum.  A friend of mine pointed me in this
direction.  I have an Epson 2000P which I currently use for color
prints using epson inks.  Well, my friend has been showing me the
light when it comes to B&W printing, to which I am also new.  I would
like to start printing some photos in B&W, but still retain the
ability to print color.  I have been doing lots of reading about B&W
printing on MIS's website, and Paul Roark's site as well.

My question is, can I swap ink carts back and forth from color to B&W?
 I have been looking at the MIS inks and would go with their carts if
I do this.  

If I can swap, should I also use the MIS color inks as well?  Also,
what is the best way to store an opened ink cart?

I also have an Epson 870 and a new R220.  My 870 is still working
fine, even though it has seen lots of use.  I plan on converting one
of them to B&W only printing as well.

Thanks for any help you can offer.

Andrew