Took my bass to get repaired last week...

[Chili]

last week (friday) i took my bass down to the local guitar shop for the guy there to have a look at it, i told him that when i hit the open E, slap it, the kneck rattles, and i cant lower my action becouse i get alot of fret buzz so i have to keep it really high, and that i have been adjusting the truss rod etc, but of course when i tryed to show him the kneck rattling you could hardly hear it, typical lol, anyway, he looked at the bass and sed it looks alright, and stood it upright and sed, the kneck has warped, what does it mean when the kneck is warped?
I sed a complete -re-setup would probs be best, and now i'm just waiting till friday when he sed to ring him, and he charged £35, that sees a little steep to me, but nevermind.
are little guitar shops to be trusted with things like this? i've never taken a bass to get repaired before, i just hope they are taken care of it.