There is an often quoted phrase in relation to setting crossword clues -"you need not mean what you say, but you must say what you mean."
This phrase applies very much to this puzzle. Working from the misprints, you arrive at a name. Look up that (sur)name in Chambers and you will get a definition describing a discovery. Subtract 2 and you have to think cryptically to realise what you are looking for, and it is to be found in the position described by the Chambers definition.
The joke is not of the funny ha-ha variety but more of a practical joke, where you are led into thinking you are looking for one thing, where you should be looking for another. There is nothing in the preamble which does not say what it means.
Having said that some of the clues are funny!