I live on LI also, and did this 3 years ago. I switched to Natural Gas from oil. I did not already have gas, It had to be piped in from the street. That line was free (100') and so was the gas boiler.
I would never go back to oil.
My advice to you is definately shop around and do NOT marry the idea that you have to go with a "big name" gas or oil dealer to do your install. Local plumbers often charge much less and they do a more professional job than the punchclock hacks the big company's hire.
I was quoted 3800.00 from a "Keyspan affiliated" installer. I had to demand an itemized estimate because I couldn't figure out how it could possibly cost 3800 for the installation of a simple, straightfoward gas boiler and water heater 12' from an already installed gas line, when the boiler is being provided "free."
Under labor it estimated 2 men, 10 hours, @ 175.00 an hour.
Now... I know nonunion plumbers on Long Island don't make 25.00 an hour, and for sure no shop sends 2 high-paid mechanics to do a residential install. In addition, the quote did not include the Keyspan "required" item that the old oil tank be either removed or cut & filled, or otherwise renederd harmless. The contractor was going to skip that part. I ran inot similar issues with another "approved" contractor, and the 3rd wouldn't give me an estimate because, although they signed up to partake in the gas-conversion program, they were mainly an oil delivery/service company and instead tried to talk me into keeping oil, and using them to install/service a brand new oil burner.
Explore your gas options on the Keyspan website:
My experience has been all positive.
- heating costs cut in 1/2 over the old oil burner. (it was circa 1975) - whisper quiet. - no more oily smell in the oil burner area. -no more tank (mine was buried) or leak worries -separate WH - could take hot shower even during blackout -much smaller boiler, though now with a separate WH all takes up about the same floor space in my 10 x 10 laundry/utility room. To be fair, new oil heating boilers are also much smaller then they used to be. -option to balance gas bills out across 12 months. -can't possibly "run out" of gas
I've made more coments to your questions below.
The key to helping with the confusion when comparing gas to oil is to NOT take advice or suggestions from oil dealers OR gas companys. They have a intrest in your choosing their fuel. Talk to a licensed local plumber.
Although it's smart to have your system serviced/checked at least once a year, you'll find that gas is by far practically maintainence free. (especially boilers, as opposed to gas hot-air furnaces.) There's no sooty chimneys, no filters, no nozzles to wear out. The rest of the plumbing is exactly the same.
As other have posted, because so many high-users of fuel have switched to dual-fuel (Like LIPA and whatever manufacturers happen to be left along the Eastern seaboard) and large buildings as well as schools, etc, the cost of the 2 fuels side-by-side is negligable.
There's 2 ways to get hot water via gas. Either via a separate storage tank heated by your heat boiler's zone, or via a completely separate gas water heater. Separate WH's are very cheap and simple appliances and work w/o electricity.
With oil, you can get a completely seperate WH with it's own oil burner (expensive, almost as much as a heating boiler) or via a domestic hot water coil inside the heating boiler (which is separate from the water which circulates through ypour heating zones) or, with a separate hot water storage tank heated by a boiler heating zone.
Since your original equipment dates back to the 60's, keeping your oil boiler and converting it to run on gas would be throwing good money after bad.