i was in a similar situation a decade ago and to put it mildly i was not a happy camper, but i did it. as part of it i made notes on what i had shown the guy, dunno why i did but i was dam glad i did later. afew months after i finished training the guy up he made a massive cockup that cost the firm money and the little wanker blamed me for not training him right. it became an unholy mess involving the union, lawyers etc. my note taking saved my job and he got fired.

so my advice is keep notes and anything else you can think of to back you up.