My first oil change was also free at the dealer. I was sent a coupon for a free oil change, but lost it. When I took the car in for them to listen to my engine tick, I had them go ahead and do the oil change which they just charged to "New Car Sales".
Our cars use Motorcraft 5w20 which is a semi-synthetic developed and used exclusively by Ford. It's a pretty good oil, and one of the major reasons our cars are supposed to go 10k miles+ without an oil change. Changing your oil significantly before 10k miles is honestly a waste of time, money, and resources. Chaging out to a full synthetic arguably won't increase your engine life due to the oil we are already using is pretty good, so you may want to reconsider and save yourself some money.
I did my first oil change at 8k and even that was too early, but I did it due to having a busy schedule and trying to kill two birds with one stone.