For what you do Windows 7 Professional is not necessary. It will have some more features than Windows 7 Home Premium, but the extra features are mostly geared towards corporate clients where there is a need for remote desktop connectivity (basically the business' IT dept can connect to you PC to either install programs or troubleshoot problems), and backing up / restoring data to servers over the network.
For $325 you are not going to be able to buy a good laptop. In that price range you are only going to find laptops using Intel's Atom CPUs. They are more powerful than previous generation Atom CPUs, but not as powerful as a Core i3 CPU. They are not appropriate for heavy graphic use and will come with Windows 8.1.
Your best bet is to...