Audio Systems: replacing the factory head unit for 1998 Lincoln Navigator, ford products, lincoln navigator

Question
I am curious to know if I am going to encounter a problem with replacing my factory 1998 Lincoln Navigator Head unit. I just recently experience my factory cd changer malfuntion which is making me want to replace the head unit for a aftermarket in dash cd player. my vehicle is equipped with a built in 8" subwoofer that is ran by a factory amp, I have already had the factory subwoofer replaced with a 8" KICKER sub, I really like the sound I am getting from just 1 sub, I want to know if the installation specialist at Circuit city is going to be able to incorporate the sub and factory amp with the new head unit I am looking to purchase?

Answer
stay away from circuit city or any big chain store
you need to go to a good car audio store
yes it is possible  to replace the radio and keep the 2 amplifiers  with the new radio   one is for the woofer and the other for the 4 door speakers  ask this question before they touch your vehicle  removing the factory amplifiers  is a option but the sound is not that good or  just replace the cd changer and keep the factory system

http://www.oemautosound.com/c-150-ford-products.aspx