Don't worry, I know what You mean - I've disassembled N950 (completely) myself. Furthermore, I've assembled it back, and it's working! ;-)

What I mean't, is that I'm quite sure, that they would either destroy Your device while trying to change eMMC, or refuse to try, even when given disassembled unit. I refuse to believe, that someone so amateur to the point of inability to disassemble (quite easy) N950, could properly identify chip needed for successful swap, and perform it flawlessly, on so "custom" device.

As You've said, they have experience with generic phones, and probably, only with them.

/Estel