Snail Question

We have just completed our first pond. Its is about 5200 gallons and
we are in illinois. No fish (koi) or plants have been added since we
just completed it and the temps are chilly here now. I have decided
to let it freeze over for this season since its so late in the year.
The external pump and skimmer will be started and seeded in the
spring. At this point I have not added any chemicals.

My question is should I add snails to my pond?

Over the years of having indoor fish tanks I am familiar with how much
disaster snails can do and how fast they procreate. But Im wondering
if they would be the best type of critter for biological breakdown of
dead leaves and such during this time. Any help with wether or not
snails are good or bad and a recommended type would be very benificial
group. thx

Rick