I understand that I must provide a written declaration for importing
cash into the Ukraine, at least beyond certain values. But what is
this written declaration, is it any format of my choosing, or is it an
official Ukranian government form that I must obtain? Plus, they don't
speak English in the Ukraine, so if it is a written declaration of my
choosing, what language can it be in?

When you arrive to Ukraine, most likely to Borispol International
Airport, they will provide custom declaration forms, which are also by
the way available in English.  On those forms you can find all
information that you need. I believe you have to declare everything if
you are bringing over $1000.  When you come to the airport there will
be two types of customs, what they call Green or Red corridor.  So, if
you bringing more than $1000 fill out declaration form in English, and
go through the Red Corridor. Plus, most of the personal working at the
airport do speak English.  It is Europe, you know

You should also check their outbound currency restrictions. For
example, a country may allow visitors to bring IN up to $5000 USD, but
departing travelers can only bring OUT $1000 USD.

Trying to smuggle cash out of a foreign country is a risky proposition.