just because he is a mechanic, dont assume he knows everything.
past experience is worth 100x more then a educated guess.
keep that in the back of your mind and you will be fine.
If anything dosent look right, post it up on here and someone will help you thru.
when your putting your motor together and your keen to get it going,
dont guess / rush on something your not sure of, cause it could cost you dearly in the long run.