Good post Bubbie and Duffer, you may want to look at TQ's post on what he did to change cams and add hydralic cam tensioner on his Twin Cam engine to give you a flav for what is involved:
http://www.hdtimeline.com/harley_davidson_engine_related_issues/13001-tqs_engine_build.html
http://www.hdtimeline.com/harley_davidson_engine_related_issues/13001-tqs_engine_build.html