I've worked at NASA and in private aerospace and military space and I can tell you that the drawings, specifications, test plans, etc. do not exist in a complete package. Things that were re-used on different projects exist, but the all-up system is history. Could we build another today? We have the technology to do it a lot better, but I don't believe the systems engineering and quality control aspects could be replicated without a national mandate ($$$ and glory). It's kind of funny, the aerospace business today is a curious mixture of 40's and 50's tech with 2010 tech. Electronics and it's byproducts are pretty much on the cutting edge or beyond, composite materials are making large strides, but other things like metallurgy, mechanisms, propulsion and guidance and control stuff are rehashes of really old technology. Watch the Mars Rover landings in January, the mix of old and new is incredible.
CW