Winterizing

Hi all. I'm new at this so please excuse what may be simple questions and
may have already been asked 180 times this year.

My first year in two boats and winter is here (Denver). My boats will be
stored indoors but not in a climate controlled environment (so it will get
cold).

1) Is winterizing a necessity? They are both 2 stoke and will both need, and
get, a service after taking them out of storage and before using them next
year.
2) What should I do with the batteries, right now the boats are in my garage
and hooked to a trickle charger but no power will be available in the
storage unit I'm moving them to.

Thanks in advance for any advice

Will