I don't have much faith in service history stamps either, but it pains me that so many others still have utmost faith in it. I've seen many examples (even on this forum) of basic's like air filters looking manky as hell when according to the service book they were changed not long ago. There is no real evidence for this.
Me and my Dad service all our own cars, because we just don't trust anyone to do it. We get our parts from eurocarparts and do it ourselves on a weekend, we take our time over everything, and do it properly. A full service includes just over 5l of ACEA-C3 oil (we use GM Dexos 2, we know it's the correct type because we put it in ourselves and how much we put in) Oil filter. Cabin filter. Air filter. Fuel filter. When taking our time, which we always do, it takes about 4 hours leaving the oil good time to drain. During this time we always tidy up other bits and bobs which may be out of place, for example the undertray wasn't fit properly by whoever did the last service before our ownership. It really isn't difficult. The problem is however trying to convince prospective buyers that it's been done to a good degree. The best we can do is provide receipts of all bought parts, which we always give to our car's new owners.
So what if a stamp has the book, doesn't mean anything has been changed. Blind faith will absolutely blind you.