1) Will any SSD work with the xps8000? Standard 2.5-inch form factor SSDs should be compatible.
2) Once installed will the BIOS pick it up automatically? Yes
3) Can I mix SSD with HDD? Yes
4) Will a SATA III drive work? I presume the xps8000 is backwards compatible so would run the SSD at SATA II? Yes on both
5) Can I take an image of my current OS, install the SSD, then restore the image and boot up? Yes, if the image will fit in the SSD's space