Off the cuff Risk Assessment:-
1) Chance of screwing up without a manual :: > 75%
2) Chance of screwing up with a manual :: 50%*
Also ... chance of the tech being a "she" ::
Not sure where you got the 50% from there Geoff?!
As you say yourself:-
The term "half a chance" is a turn or phrase, an
idiom, and is not (usually) to be taken literally. Substitute the word "opportunity" if you like.

Or does the idiom only apply when you utter it?

Do NHS departments in different trusts not assist each other with information exchange?
Of course it happens. I have done so myself on many occasions. The major difference is that when it did I knew the people I was dealing with and will give them advice and help that they felt confortable with and was within the limits of their knowledge and abilities.