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 43 | Glock 26 G4 | Glock 19 G4 BFG | S&W M&P 22 | HK USP 9 | HK USP 45 (Tan) | HK P2000 | HK P30L | HK VP9 | HK 45 C | HK 45 C "Sand" | Walther PPQ 9
Daniel Defense DDM4 V4 | Arsenal SGL 21 | ASA Side-Charger SBR | Savage Mark II FV-SR
Mossberg 590A1 20" SP | Mossberg 500 Cruiser