Ahh, so its an XPS 730x. Well yes the board is still swappable. The the XPS 730 and 730x cases are identical, with the 730x having the additional theatre lighting inside when you open the door and no power is plugged in. That is the only difference really.
I had the 730x with my Asus P6T V2 inside. I think I have some pics up on the forum somewhere from when I did it. And as far as I know, there is little to no info or threads that swap the motherboards with the 730/730x. Ive searched countless hours and came across nothing when I was doing it myself. I just bit the bullet and did everything, and figured out for myself.
The only problem you may encounter is with the H2C Cooling Unit, if the system has it. The cooling unit has the CPU block and a chipset block. The CPU block will fit any motherboard, but the chipset block will not, and will only fit the stock board. Also, the cooling unit cannot be disassembled because it is pressurized. But you can always rip it out and use a regular fan/heatsink instead. And you can fit a Prolimatech Megahalems with a good amount of room to spare.
Here was one user with the XPS 730 that did a swap here: viewtopic.php?p=26707
Basically though, its the same as a 630i. Everything is ATX. The only thing that will not be able to be swapped is the PSU, or no MIO board functionality. It uses a wierd proprietart 10 Pin cable that no standard PSU has. But the PSU is upgradeable to an Alienware 1.1KW PSU if needed, as they are the exact same dimensions, and use the same cable connection to the PSU, and MIO board.
Let me know if you got any other Q's Doc. I am glad to help anytime.