I think that the reason why the board haven't got the footprint is because this boards for agilent aren't troubleshooting so you have a fault and you replace it by paying thousends of dollars. Dave have you looked at this addition service manual contents?
LINK: h**p://www.home.agilent.com/upload/cmc_upload/All/35670-90067_supplement.pdf, there some more content in there. Probably the schematics will be avaible as soon as the instrument go out of production.
If you really want to repair it try to ask to agilent If they gave to you the schematics, somebody in the world should have those either a repair center or agilent itself.
Have you tried to put a signal in?
Apparently in new revision the instruments use only one cpu board, I've read that on the supplement manual somehere If I recall correct.
Best regards, Alberto