Digital BW, The Print

I had a clog in my 1160 that I could not clear but had to close the 
printer down for 2 months.  I'm using the old piezo inks with CIS.  
Now I'm back to work and can't get any pattern in the black position 
or in the cyan position when I do a nozzle check. The strange thing 
is I can see some air spaces in the ink line to the black cartridge. 
How would I clear that out?  Do not know how that happened. Since I 
can't get even one mark when I do the nozzle check, do I REALLY have 
a print head problem?  

Have any of you had to replace print heads?  What did it cost? 

I bought this set-up from someone else and I have gotten some nice 
prints from it. I'd like to get it back up and running.

Billie