"Network Recovery" Help

I have been given permission to test a network's security at a school I am currently going too. I already have access to the local network and I plan on using the packet sniffing method to "Recover" a "Lost" Password to the server application running the school's vending machines. I need to know a few things though.

I am using Cain & Abel to packet sniff. Is there anything better?

What would be a good data replay application to use with "Liberated" Packets?

I am pretty new to technology, I know the basics but haven't really delved too deep into the rabbit hole yet. I'm prepping for my MCSE MCSA Exams and would like some firsthand experience with "Network Recovery"

Thanks for the help in advanced.

Op here

before I forget

I'm running windows 7 (64x)
If I could help it I'd rather not have to change my OS for an exercise although I could always quickly set up a dual boot if I really needed Linux to do this.

Use Wireshark. It take some time to get used to the application, but it offers a lot more control than Cain.