Quick question, will this processor work?
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewI...RK%3AMEWNX%3AIT

And if it does, how do I add the switch like the one on the DreamX for 744Mhz Mode?
And should I get some kind of socket instead of solder it directly? (Which socket do I need to get then?)

I don't think so. It's not that easy to upgrade the processor of an xbox.
I believe the guy who used to do it used a special socket because some of the cpu pins where different.

The xbox cpu is a bga soldered to the mobo. You need some special tools to remove such a chip properly, and even more special equipment to place something else back.
They sell some stuff which is called a bga reballing kit. It contains the tiny solder balls that are needed on every pin surface so that it makes connection to the pcb again after soldering. If the chip isn't equally heated when it's resoldered, it will bend slightly, and some of it's pins won't make proper contact.

You might be able to remove the chip with a heatgun, but your mobo will be electronic waste afterwards.

I think the cpu's he used are mobile pentium 3 processors that run at 1400 Mhz, and not P4's or celeron's

regards.

Yep. Here is your info.