think about it, you really dont know who is installing the parts at the dealer. i rather do it my self so i know everything is done right, and check it 3 times to make sure i got everything.
personally i think the guys that work at the dealer can care less if they did it right or wrong, i remember my dumb ass cousing keeps paying for everything he gets for his altima, he paid like $150 to get his Intake
install, and we i checked to see if everything was right, his filter was not even on. i was cracking up, his engine was sucking all the dirt and shit, then he got his header put on, and they forgot to do one bolt, keeps getting worse he paid to get some bulbs install, and his headlight got condensation all over it. i will never trust a shop, i would have to know the person who works there before i pay them. just my 02