Don't candy-coat it for him, Tom, tell him what you REALLY think!
_raj- You can come up with a pretty-good estimate of what a new system would save you by using the FSC (fuel savings calculator) downloadable from a link halfway down this page:
http://www.nora-oilheat.org/site20/index.mv?screen=home
Using that tool carefully can also determine the whole-house heat load which can allow you to "right size" the boiler, resulting in the highest possible efficiency.
With a right-sized (or smallest-sized, as the case may require) new-school oil boiler you can probably peel off 150-200 gallons of fuel use.
But new boilers are expensive. You'd probably get a higher return on investment out of a high-efficiency ductless mini-split heat pump (air conditioning + heating), and just adding an economizer control to the boiler, such as the Intellicon HW+. (For a discussion about how a mini-split economics relative to oil boilers
see this thread. ) Assuming the boiler is 2-3x oversized for your actual heat load (which would be typical), you can expect about a 10-15% reduction in fuel use out of an economizer control. If you have high-mass radiation (big old radiators rather than fin-tube baseboard) you might use an "outdoor reset" type control instead for similar return. With this type of control an 80% boiler will run at least 70-75% efficiency (rather than 60-65%) even if it's monsterously oversized. Thats 10-15% reduction in fuel us for a ~$500 investment (installed price.)
But depending on your electrical power rates, a decent mini-split heat pump will cut the heating cost by 25-75% from the cost the current price of oil in an old-school boiler, at an installed price of under $5000 (assuming a single-head 20,000-24,000BTU heat pump.) They get excellent efficiency above 25F, pretty good efficiency down to about +10F, and OK-efficiency down to -10F (at least some models do.) A mini-split isn't likely to be able to handle 100% of the heat load (unless it's a small house with an open floor plan), but if you can push 2/3 of the heating load onto the mini-split, that's 2/3 of the heating bill that comes at a big discount, decimating the oil use, but boosting the power bill (but by less than the cost of displaced fuel use.)
But if you're fortunate enough to be on a natural gas main and have higher-than average electricity prices it can often be cheaper to heat with gas.
But maybe oil is going to fall back below $2/gallon for then next decade, eh? ;-)