Don't think they are quite as rare as you'd think. Got hold of one about a year ago through the UK group, so they do come up every so often. (think I had to pay about £800)
Swapping them over wasn't quite as bad as I feared but I had that sinking feeling the first time I turned it back on and nothing worked.... Probably the hardest bit was the pop bumpers. Didn't help that I tried to do it when the kids were away for a couple of days and ran badly out of time so then had to do it in small stages over the next 4 weeks+ which meant I totally forgot where everything went and the bloody cats kept playing with all the wires.