Q: I have a macbook pro that was a snow leopard I updated my software to Mountain Lion in hopes of getting AirPlay to work on my Apple TV however the icon is not on the top bar like it should be. Any help?

http://support.apple.com/kb/HT5404

About AirPlay and Airplay Mirroring

AirPlay Mirroring requires a second-generation Apple TV or later, and is supported on the following Mac models: iMac (Mid 2011 or newer), Mac mini (Mid 2011 or newer), MacBook Air (Mid 2011 or newer), and MacBook Pro (Early 2011 or newer). For non-qualifying Macs you can try using Air Parrot.

Several Apple Articles Regarding AirPlay

Apple TV (2nd and 3rd gen)- How to use AirPlay Mirroring

How to set up and configure AirPort Express for AirPlay and iTunes

About AirPlay Mirroring in OS X Mountain Lion

iTunes 10- About playing music with AirPlay

Troubleshooting AirPlay and AirPlay Mirroring

Using AirPlay

The first part refers to Airplay Mirroring. I don't know what other limitations there may be with respect to minimum hardware requirements. But the links provided should help you find out.

I couldn't say. Maybe reading the instructions on setup would help.