Heck if you have an oil leak, you have a mess or maybe a fire. If you have an gas leak all you have left is toothpicks. Now what do you prefer ?
As Lytning said, we have a saying here in Maine, "Oil wipes up. Gas blows up." I do both, alot, and I am way less nervous on a 4 million btu boiler burning oil than I am on a 4 million btu boiler burning gas. Just saying.
Here gas is $.35 a therm (100,00 - 110-000 BTU), Oil is $3.99 a gallon (144,000l BTU) Do the math. No wonder we are doing so many oil to gas conversions. 40 years ago it used to be the other way around. Oil was cheaper than gas.
If you really know how it works, you have an execellent chance of fixin' er up!