Ross
There is one sure fire way to do this on any inkjet (as far as I know). But
firstly check to see if the tool box for the printer allows you to replace a
non empty cartridge (some do).
If that is not the case then....
Power the printer on, if the head starts to move toward the centre (you should
hear it) immediately turn the power off at the wall socket (or pull the power
connector out of the printer). The head carriage will then be free to move on
the carriage bar, so you can lift the lid and move the carriage to the correct
position and do your thing! A few printers do not move the head during power
on. In that case make it print and pull the plug while it is printing, this can
increase ink usage but in your case that isn't a problem.
When you have changed the cartridge just close the lid and power on and if
there are a few strange noises just ignore them!
Check to see what the computer reports for the ink levels in the printer, if it
is 100% or close to that then all is OK, otherwise download the SSC utility
from
http://www.ssclg.com/epsone.shtml and reset the colour ink levels after
setting the utility to match your printer.
Good luck
Tony