Wow , you don`t trust the dealer to do something as simple as an oil change ? I took my car in for every free 5k check . They only will do the free changes at the 10k interval . But I did the in between ones at 5 and 15 k . They also rotated tires every 5k and do a multi-point inspection that was free . If I were you I`d take advantage of that.
I don't trust the dealer I use at all, but since it is free, I deal with it. I just double check their work.
Example why I hate them: I specified before they changed my oil to not leave oil on the engine cover. I got the car back after service, popped the hood in the service drive, oil all over the engine cover (even seeped down onto the valve cover). I grabbed a rag that I had brought with me because I knew this was going to happen. Cleaned it off right there in the service drive. I emailed the service director about the issue. He said that they are very busy and things like this can be missed. It has happened every single time, so it's clear to me their problem is not being busy. They are being lazy and sloppy with their work.
Also to note: I came in for an alignment check, they ended up adjusting it. I got a flat a few days later and both wheels on that side of the vehicle were not torqued down. I could tell even with just the stock lug wrench when comparing each wheel.