Implications of resetting Postgres service in Windows

We have Postgres 9.4 installed on Win2012. It was installed by an
outside contractor years ago.

I was asked to review and change all the passwords used in Postgres
(along with another product) and noticed that on this server, the
postgres service "postgresql-x64-9.4" runs under the "Network Service"
account and it has a password associated with it.

I sort of think I can guess the password used by the developer, but I
cannot be sure.

If I change this password, what are the implications:

a) nothing - the password is only used to secure the service running

or

b) the password also needs to be changed somehow within the database
(using pgAdmin I assume - although I have not found a screen there to
change the superuser password).

Any suggestions would be appreciated! I just want to update the
passwords as per higher management but not knock out the server!

Thanks.