I ordered a replacement xbox motherboard from xboxbreakers on the Thursday evening and it arrived first thing on Saturday morning.
It looked brand spanking new - Im amazed it actually came off an old xbox, and already had the pin header sodlered to it for ease of use.
The emails I sent were answered honestly and fully and as such was very, very happy with the service, and will definietly use them again should I need to.
They also offer a service whereby they may buy your old knackered board off you, though obviously (Id guess) any price offreed this would depend on damage and repairablilty.
Having said that, if your buying a new one your old one is obviously fubar'd so any monies from the knackered one should be a bonus!
Quality and def. use again