I assume you are talking about electric to gas FURNACE?

I have had both and vastly prefer gas heat. It just feels warmer to me, plus I live in a small town where gas is cheaper than electricity.

I considered it, but decided that electric would turn out to be cheaper over the years. If the house has an electric furnace or heat pump (i.e. with ducts and vents throughout the house), the change to LNG is probably about $10K, but if it's heated by electric baseboards, the cost will be dramatically greater (because there's no ducting)

It depends. Is it a newer system? Is it a heat pump? What zone are you in? Is it sized accordingly? Are your windows and doors well sealed? How's the insulation? Too many variables to give you an answer with so little info.

Is the home already plumbed for gas? In my home gas is no already plumbed, and it would cost north of $10K just to run gas from the street to the house

I’m in the south so we basically always use heat pumps. They are very efficient but of course we are mainly focused on AC!