Publishing someone else's app in the play market?

Question

Google

There is a third party service that provides us with the application. The application is generated when the main program is installed, that is, the main program in the form of a server, on our computer. The bottom line is that the application that generates the server has already been published on the Google Play Market, but we need to change the icon, change the name, and publish it on Google Play. Is it possible to do this? As far as I understand, Android APK applications are signed with a certain key. to publish a modified application Whether we need to re-sign it. If you need to re-sign, do you need the source code, or can you sign the finished built application?
At the moment I'm looking for a person who can do this, that is, change the application icon, and change the name. You also need to publish it on Google Play.