you always appreciate an engine more when you've rebuilt it yourself.
i bought a 200SX (1.8 turbo) and it turned out that the turbo died on the way home and that one cylinder was low on compression. i've not rebuilt an engine before. i only did this as i had time on my hands and not enough cash for someone else to do it.
in this day and age its alot easier to do. when ever i had pathetic little problems i could ask for pictures and advice on the owners club
its all so fookin easy to do when you think about it. more people should do it. i can understand the worry, especially with expensive engines. they are all similar once the sump is off.
don't knock people that do it themselves, they often do just as good a result if not better. (as you tend to take more care and double check everything)