Last summer, we purchased a 13 year old house with a cedar deck. While
replacing a few of the deck boards this week, our contractor noticed
that the deck is attached directly to the vinyl siding without any
flashing installed. He said the only way to save our our sill plate
from rotting is to rip the entire deck down, install the flashing and
rebuild the deck. Is there an easier and less costly way to reduce the
possibility of rot without ripping everything down? We live in Central
NY, so we do get a good amount of snow on the deck each winter. Thanks
in advance.

Contractors tend to suggest radical solutions, as it makes for bigger jobs.
I've handled this situation by sawing a foot or two off the deck - assuming
yours is not cantelevered off the house - and pulling off the siding, then
structurally tying the deck joists to the house, and flashing and re-siding.
There is also galv. stand-out or hold-away hardware that keeps the deck wood
from touching any of the house, which is ideal. Susggest you consult a deck
building booklet at a big box store, and get the elements of proper deck
building. Otherwise, contractors may take you for a ride.