Q:

Sign and update Visual Studio Extensions

So it seems as a pretty easy Task, I created a VSIX which I uploaded a few days ago.  Some days later I fixed some issues and now I want to update the extension on the marketplace. 
I went ahead and took a look at the MSDN which states the following:

Unsigned all user extensions do not get updated automatically.  You should always sign your extensions. 

So therefor I went on an tried to sign my VSIX as explained here.  Which tells me to do the following:

Search for VSIXSignTool from VisualStudioExtensibility and install the NuGet package. 

After downloading the package, I searched for the given location which should be in your project's local packages location.  Which makes me wonder, cause I do not have any local packages folder for this project.  Furthermore I should sign my extension with the following command:
VSIXSignTool.exe sign /f <certfile> /p <password> <VSIXfile>
Which makes me wonder, what kind of certificate that should be, what should be the password be, a new password?  
Anyway, lets assume I somehow mange to do that, how would I 'update' the extension than?  Just upload it again as a new package with a new VSIX-Id? 
To sum it up, this are my questions:

How/Where do I download the VSIXSignTool
What parameters do I need to pass into the VSIXSignTool command provided above
How do you really update the extension on the marketplace and do I need a new VSIX Id

A:

I suggest first try to update your extension without signing.  Just increase the version number and on the marketplace site click Manage - ... (More Actions) - Edit - Upload Extension/Edit package. 
VSIXSignTool requires a code signing certificate that needs to be purchased.