egg yolks

[personman]

Hi: I have a few questions about the venerable egg yolk:
(1) are there any nutrients LACKING in egg yolks that must be derived from other sources; ie. are they a "whole food" sufficient by themselves
(2) how does one preserve egg yolks to avoid oxidization of cholesterol(eg. air tight containers; in fridge, etc.)?
(3)  what should be added to the diet in addition to eggs if one wishes to go vegetarian(I know: blaspheme!)