I hate that feeling... You just know everything will end up needing extra this n that, re-boarding etc just to confirm their thoughts in their eyes at least..
I'm sure everything will go fine, all you can do is explain the situation and show your knowledge of products etc and if they pick you based on that then you just do your job!
I did a job once and had the exact same feeling, and similar situation with the reboarding
I explained I would try to save the substrate etc but was unlikely,
Long story short I ended up paying for the quality gear I needed rather than the cheap stuff they wanted out of my pocket just for my peace of mind!!!! Aghh never again tho!