Noob questions about upload & security
Since you have app in C:\myap you need to run appcfg.py update C:\myap. It's just a path to you app on your machine.
In windows command line. For example, "C:\Program Files (x86)\Google\google_appengine\appcfg.py" update C:\myap
No, appcfg uses SSL while uploading. It's safe.
If you mean to call application uploading - it's not really safe. I don't know why you need this. You can add app developers in App Engine admin console, so they will be able to deploy application from their accounts.
I have the myapp.py and app.yaml in my windows C:\myap directory.  The docs say to use:
     appcfg.py update myapp/
to upload the app.
I've downloaded/installed Python and the Google python kit.
Sorry, for these noobish questions, but:

Is the myapp/ listed above refer to c:\myapp on my windows machine?  Or is it the name of my app on the google side?
How/where do I type the appcfg.py to upload my directory?
Are there any security issues associated with using my gmail account and email address?
I'd like anybody from Second Life to be able to call this from in-world.  There will be about a dozen calls a week.  Are they going to have to authenticate with my email/password to use it?

Thanks for any help you can provide!