Improve the bracketed part of the sentence.
The guide's (knowledge) of the history of the monument surprised me.

The noun 'knowledge' is perfectly correct in this context. It describes the deep understanding and information the guide possesses about the history of the monument.
'Familiarity' usually takes the preposition 'with' (familiarity with the history).

'Know how' means practical knowledge on how to accomplish something, which is inappropriate here.
Therefore, no improvement is needed.