Newbi to the A1278 Need info

Been playing with computers for quit a few years but am new to the whole Mac experience, issue i have , I have a mid 2010 A1278 with a logic board issue that is being replaced, how do i know what Operating system should be on it, and where would i get it if i need a copy, looked around Apple's website but not seeing anything, also do you load it the same as windows on a non mac computer ???, any info would be good
Thanks

That machine can run Snow Leopard, Lion, and Mountain Lion. Your choice, but you need at least Snow Leopard 10.6.6 in order to access the Mac App store to buy and download Mountain Lion.

I would recommend getting Snow Leopard, updating it to 10.6.8, then use the Mac App Store to buy and go directly to Mountain Lion.

To get a copy of Snow Leopard, you must CALL Apple on the phone and order it ($30). They will send you a DVD. Mountain Lion is download-only, and costs $20.

thanks for the info guys,appreciate it