D-Rock
The entire venting/chimney needs to be replaced. this is the most crucial part. gas appliances use "C" and "B" venting materials, which are single walled tin, and double walled tin respectively. these are not sufficient for combustible solids. Burning solids requires an "A" vent. this is similar to a B vent but (it's been 10 years since i read this) it has a layer of insulation inbetween the pipe walls to keep the heat inside the chimney, and are much more air tight. Call a professional wood burning stove installer, and they will do it PROPERLY. "A" vent is VERY expensive, (you could spend as much on the venting as you do on the stove) and you don't want to make any mistakes, or do it incorrectly. removal of all of the other venting materials should be done before they get there to reduce cost.

Louis C
Go to home depot rite up by the check out counter there is a book shelf full of D.I.Y. books find the one on chimneys it will show you what is involved. It can be done its a lot of work.