Its actually not too bad. Just go ahead and unplug that antenna and work its way out , but b4 you pull it out of the pillar make sure you tie a string strong enough to it. Go ahead and proceed to pull it out. Take the string off the old antenna that you tied and tie it to the new one. Obviously use the string to help you get it through but like I said make sure the string is strong for the force you will put on it. After its through you can either follow the same route to the radio or make your own.
