You can check what service pack is applied in Project 2010 through:

File > Help.
On the right side click the link Additional Version and copyright information
At the top of that dialog you should see:
SP2

Regarding the difference between Save and Save As. A Save is incremental adding only what has been added to changed to the file. A Save As is a completely new file, calling on the network to create a completely new file and using more resources.