aapt adb android shell

How can I launch and execute Vending.apk on the Android Emulator from adb

I’ve been trying to install Vending.apk into my emulator w/o success. It says it already exists and fails to replace it when I use adb install -r. The icon does not show up on the screen so I can’t tap it to launch the Google Play marketplace.

Therefore, I thought I could run it from my PC (MacOSX) using adb like this:

adb shell am start -a android.intent.action.MAIN -n

I constructed the above from examples that work in this article:
How to run (not only install) an android application using .apk file?

And I unzipped the AndroidManifest.xml file using info from this method to see if I could discover the activity name, but no luck:

aapt dump xmltree <apk-file> AndroidManifest.xml

I guess I need to know the exact command to execute the vending apk because I can’t seem to find the correct Activity class. adb shell am start keeps giving me error type 3, Activity class does not exist.