My next door neighbor has a Fisher stove. The Rolls Royce of stoves in the 80s. But when she damps it down it shuts off all the air and the wood smolders... and smokes. When the EPA regulated woodstoves, Fisher went out of business. As did 90% of stove manufacturers. Now there are some great old Vermont Castings stoves still out there as many of my neighbors have had them since the 70s. But most of the old steel stoves are better off scrapped. Parts are a major problem with the defunct brands today and then some amateur jury rigs a repair and the house burns down.

As you already noted, the smoke comes from colder, heavier air pushing the smoke back down the chimney. The fact that you have an external chimney doesn't help either. For its use right now an outside air kit would probably not help much. I would seriously look at an insulated metal liner but only if you dump that older inefficient rather dangerously installed insert for a newer clean-burning insert, like maybe an Avalon Olympic. I have a small freestanding wood stove in a chimney like yours with an insulated liner and it drafts like a charm. I burned two cords of wood in it last year, swept the flue this past weekend and had less than a 1/2 gallon of very fine soot in the liner.

I had a Pacific Energy insert installed in a 55 year old home last spring for $3600 including some chimney repairs and a full stainless steel liner. It heats fantastic- with an insert a blower is a must to get efficient heat. My heat pump hasn't kicked on yet and we've been in the 20's a couple of times. I agree that spring would be best. This is the exact worst time to buy a wood stove/insert as everybody and their uncle are considering the same thing. Go ahead and take that tree down and split that wood, though. It won't be ready to burn until next season anyway, so use the time betwen now and then to research inserts. A lot depends on your existing chimney and the size of your fireplace- I would schedule an inspection and an at home consult to narrow down your possibilities, then hit the web . I've included a link to a very busy forum that can give you tons of information and suggestions. They will likely ask for a photo of your fireplace so get one ready. Here is a link that might be useful: Hearth Forums

thats what i did (or had done) cap the gas line as low to the floor as possible, shut it off, and insert wood.