It took alot of work and fanagling to get everything in properly.
This person must be pretty unfamiliar with the gun and you probably would have done just as well to install it yourself. I've done 3 of these and they are a piece of cake. There's nothing to specially fit... just drop in parts. Not sure what was so difficult. But yes, the DCAEK kit is a spectacular upgrade to the M&P.
I did a review as well about a year and a half ago:
Glock 17 G4 FDE | S&W M&P 22 | S&W M&P 45 | S&W M&P 9 | Sig P226 MK25 | Sig P229 Extreme | Sig P227 Carry | Sig P320 F | Sig P320 C | HK45 | HK 45 CT | HK USP 9 | HK USP 45 | HK VP9
Daniel Defense DDM4 V4 | Arsenal SGL 21 | ASA SBR | Savage Mark II FV-SR
Mossberg 590A1 20" SP | Mossberg 500 Cruiser