1994 Lincoln Town Car Heater core cost and replacement

I need to replace my heater core in my 1994 Lincoln town car. I took it to my friend who is a mechanic because all the windows were fogging up and had a sweet odor in the car, he said the heater core was bad. I just have it bypassed right now. I was wondering what the cost would be in labor to repair the heater core. Also how much it would cost for labor and parts all together. I was also considering doing it myself with a haynes manual, I have done routine repairs on my car before, brakes, fuel filter, etc. and was wondering if it would be a good idea to do it myself, and how long it would take.