LOL … clearly not a question to ask Terry. If the question contains the words “or should I just get a Mac” the answer will usually be “GET THE MAC!” 😛
To answer your question so you can make a better decision (and I agree with Terry that, given the chance, a MacBook is preferable for DJ/Sound work), here goes:
1) I don’t know about Serato specifically, but I know other software has options so either manually set file locations and/or search for files that have been moved. So, after cloning the operating part of your HDD to your SSD and hooking up your HDD as an external drive, you should be able to get it all back on track. Question: How much music do you have? We are at the point where 256GB of SSD is relatively “cheap”. So, unless you have more than say 200GB of music. I’d opt for getting the bigger SSD and keeping everything on there.
2)Win 8 vs Win 7. In my option that would be up- not downgrading 🙂 Apart from the legal issues (you can’t buy Win 7 anymore, so unless you can find a license used somewhere, you are out of luck), I’d go for a Win 7 environment. Whatever version of Windows you use, I am an avid supporter of dual-boot systems. The DJ boot environment I would strip Windows as much as I can (there are plenty of manuals/instructions online to do just that).
Good luck & greetinx.