Ah well, I've just been qouted £50 to have it fitted so I'm going for that option. Something will go wrong if I do it (loosing gearbox oil etc) and it will probably end up costing me more! I've saved a few qiud by doing both ball joints for only £20 and the MOT was only £25 with the retest free.
One more question, they reckon that the tracking needs doing after everything has been apart, it won't do any harm really, I've never had it checked. But is it really necessary?