Digital BW, The Print

I've gotten some ink blotches, round, on a couple of prints with Lyson
inks cartridges, and another bit of excess ink at the beginning of
printing on one print.  Had this problem with MIS cartridges and Lyson
too, so I'm thinking it's a printer head.  No problems with Epson
inks, however...Hmmmm

Can anyone enlighten me on the probably source of the problem, and
tell me how to get (and install?) new printer heads...or should I just
buy a new one...

PS love my 2000P I must admit as it prints well in black only, great
in color, slow as molasses but reliable. 

Dave