The way to know whether you can use an insert in your existing fireplace is to read the installtion manual for the equipment you are considering. It should tell you what kind of fireplaces it can be used in.

You should read and understand that yourself, perhaps with the assistance of a sales rep, but I think you are correct not to take a sales rep's assurances at face value.

A wood stove will probably give you somewhat more heat than an insert, but I don't know whether the kind of installation you are suggesting makes sense. The combustion gasses from a wood stove can be very hot, so wood stoves need to be vented as described in the installation manual for the equipment as well.

Wood heat can be cheap, especially since it sounds like you can get wood for free or at low cost. But it tends to be a lot of labor, and rather dirty. A lot of people get tired of the work after two or three seasons.

Cutting and splitting wood especially is a lot of work.

Thaink carefully about how much work you are willing to do to get that "free" heat!

We installed a Jotul direct vent gas insert into our prefab fireplace last fall, and are quite satisfied with its performance. I'm convinced that direct vent technology is the way to go. It's the most energy efficient and safest. In our experience, it throws off a lot of heat, that we need the remote thermostat. The remote is better than the one installed in the wall, in my opinion, because you can experiment with where to put it for the best result.

There are several fireplace and fireplace insert dealers here in the chapel hill/research triangle area. I'm sure there must be several in the Piedmont area also. If not, take a drive out here and scout around.

About going from wood to gas: We'e retired and in our early 70s. The only use we got from out 1985 vintage prefab fireplace was a small fire with fake logs you get at the supermarket. I quit making real wood fires because they're too much bother for me. But we need a really good source of heat for those rare occasions when an ice storm cuts the power off. We got it and we're glad we did. But direct vent gas systems are not cheap. I haven't figured out how much gas I'll have to save before pay-back. I just decided I wanted it and needed it. I didn't want to spend big bucks on a stand-by generator that I would use only once in 4 or 5 years. At least with this, I have something we can enjoy every day in winter. Does it throw off heat? Just give it a few minutes and it feels like a blast furnace. But it's radiant heat, so you have to be near it to feel it. Some kind of air circulating assist will distribute the heat effectively, but of course they will work only when the power is on. Oh well, you can't have everything.

Good luck with your search and decision.