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.