So here's how it should happen
1. Buy a backup drive. Your best choice is a FW 800/USB3 so it will still be useful in the future and give you solid performance now. However, if you are really, really short on cash, you can just get a USB2 or USB3 drive and not worry about Firewire. Depending on what you are doing, it might not make a huge difference. Those of us who use video, transfer huge files, and edit always want the fastest transfer speed and fastest drives.
2. Use TimeMachine to back up your entire harddrive
3. Have them replace your system drive and restore with TimeMachine. This will restore all of your hardware, current operating system, and programs. The trouble comes if you are using more space on your current system drive than your replacement. That means all of the files won't fit on your new drive and that is a huge hassle! How much space are your current files taking up?
But you DO want an external enclosure (very inexpensive) for the drive they take out so you can still use it. Something like this
http://www.amazon.co.uk/Inateck-Ext...&sr=8-1&keywords=external+2.5+drive+enclosure
Finally, the 8GB RAM upgrade will help a bit with speed on your computer depending on the programs you are running (like Photoshop)