Disconnect the dampers/heads first, then install cleaning carts. Pull cleaning solutions through the lines with a sryinge, and let the solution sit in the lines for a while. this will help get dried ink out of the lines and hopefully out of the needle as well. you'll need to manually (or through the service menu) open the valves.
you can then remove the cleaning carts, put in ink, and either manually or through the "fill up ink" menu, recharge the system. its not a good idea to leave ink in the system for months on any solvent system, but with some babying, you may get it mostly back.
Sightline's suggestions for massaging in the head back to life will probably be necessary as well.