For my answer to the "20 year estimate" I suggest you read my reply to your comrade Jon Ellison. Needless to say, the Egyptians of the Old Kingdom were more than capable of quarrying, hauling, and setting limestone and granite blocks, and were quite adept at erecting monumental structures.

Something that is often conveintly forgotten by the fringe (dare I say perhaps a little too conveniently) is that contest to popular misconceptions, the Giza pyramids didn't suddenly appear along the edge of the Libyan desert out of thin air without any prior precedent. Scholars have traced the progressive evolution of Egyptian mortuary architecture over a period of centuries beginning with the simple pit graves of the Predynastic period. In light of developing theological beliefs being advanced by the solar cult of Heliopolis, the true pyramid form was in fact the logical pinnacle in a progressive sequence of mortuary architectural development.

There is a wealth of Egyptological literature out there. And I can assure you, that your mind will be better served by reading it rather than the works of von Daniken, David Childress or any of your other fringe favourites.