Gas and Oil Home Heating Furnaces - What should be the reasonable cost for converting OIL to GAS?

I have a small 2 story house (800 sq. ft. with 2 bedrooms, one bath). I want to convert OIL to GAS. Called in several plumbers. They all said they provide "excellent" service. But the price for removing the old boiler and installing a new gas boiler and a water heater vary a lot. It ranges from $4,500 to $8,000. That should include a chimney liner for the water heater. I really get confused what is the reasonable price.

I'm also thinking of replacing the radiators with baseboard heaters, not sure about that price, either. About 6 pieces of Baseboard heaters needed, each about 6 - 8 feet, in addition to a small one in the bathroom.

It kind of depends on what question you ask of the bidders and how they respond.

What is "reasonable" is going to depend on a lot of different factors including where you live. What may be "reasonable" in one part of the country for some very specific equipment and labor may be a steal in another part of the country and also be outrageous in yet a third part of the country.

I recently took bids on a replacement gas forced air furnace. The bids ranged from a low of about $2,500. to a high of just under $4,000. I made it clear from the get-go that I wanted bids for straight-across replacement, I specified the BTU size and efficiency and there were no "add-on" improvements to my basic system.

You need to educate yourself as to what is "out there" in the way of equipment and make some informed decisions concerning just exactly what you want and then draw up a "bid specification" sheet to give to all bidders. Only when they are bidding for the same system (albeit they may specify different manufacturers) can you truly compare the various bids.

Now-a-days depending where you live the conversion from oil to gas may also require decommissioning of the oil tank. If it's a UST (Underground Storage Tank) you may be able to abandon it in place (cut, cleaned, inspected and filled with sand or foam) or may need to have it removed, especially if there is evidence of a product discharge into the soil - which will require costly testing and remediation and formal reporting. An oil heating system is more than just a boiler, some pipes and radiators - it also includes a tank, and that issue can not be ignored. I suggest you check with your local building department and find out about the local and state laws that will apply to your tank.

Thank you all for your replies.
I am getting closer to signing the contract. I am planning to redoe everything, including digging out the oil tank. I believe anything below $10,000 will be "reasonable". More expensive ones offer more warrenty.