On mined I had to run threw the ceiling on one and the other threw the duct. As stated, drop the lights, speakers and you can see enough to pull the cable. You do not have to take the wires loose on the lights and speakers, If in the duct just pull from the front to the rear and then reseal the ducts where they come out on each end. As Doug stated they are wired straight and here is a manual if you don't have one. If you know someone who pull wire, see if you can use there pole and it want take but a few minutes to get the wire threw, If not just tye them together and gentle pull. You will need a crimp tool to put the ends on. You must disconnect from the roof of each AC unit.
Remove the one on the rear first and pull to the front, might help with two people.
http://www.dometic.com/b3056cd0-1a5b-4a15-8c1f-1d322d4ac84d.fodoc
