First, I assume you REALLY mean ISO 9001:2000 as your registration goal, with element 7.3 (Design) excluded.
ANSI/NCSL Z540-1-1994 was issued in August 1994. This standard includes all of the requirements of ISO 9001-1994 and MIL-STD-45662A; and SOME of the requirements of the old ISO Guide 25. It is reorganized and restated to (supposedly) meet the needs of a calibration lab.
Also in August 1994, the Department of Defense cancelled MIL-STD-45662A and replaced it with Z540-1. (Section 18 of Z540-1 IS the old MIL-STD, almost verbatim.) The MIL-STD, and this part of Z540-1, applies to the measurement standards used by a calibration laboratory.
ISO 17025:1999 completely replaces Guide 25. This goes beyond any of the other standards. You have all of the quality management system requirements of an ISO 9000-based system, PLUS the requirement to demonstrate your technical competency in each measurement area being accredited. You also must have a very strong understanding of your measurement uncertainty for each process, as well as good measurement quality assurance processes.
ISO 10012-1:1992 is a useful addition to these standards and ISO 9001:2000, for quality management systems as they apply to a calibration lab. At almost ten years old, though, it is somewhat dated.
I'm going through registration now, and it is a lot of work. I echo the suggestion of Ryan - look at all of them. ISO 9001:2000 will be your main guide as that will be your conformance standard. If you are involved in calibrations, though, then you should ALSO be doing elements from Z540-1 and 10012-1 that are not in 9001:2000. Once you have an effective 9001-based quality management system in place and registered, then you can re-assess your needs to see if laboratory accreditation under 17025 makes sense for you.
Graeme C. Payne
ASQ Certified Quality Engineer
[This message has been edited by Graeme (edited 05 June 2001).]