You should introduce yourself in the "Welcome New Member!" section of the forum. Regular oil is changed on average every 3,000 miles. Synthetic oil is changed on average every 5,000 miles. You should change the factory oil at around 5,000 miles
I have taken my to the dealership, so Mitsu knows I have been keeping up with the schedule maintenance of the 08 in case of other recalls and what not.
If you use conventional oil...It should be changed every 3000 if you care about your car. If you use synthetic (depends on synthetics if its class 3 or 4)...class 3 are hydrocracked syn oils......class for are PAO syn oils.. you have a few thousand more to change it. Typically from 4k to 6k. Some say even more I changed to syn from my first oil change. Changed to Mobile 1 EP and I change it every 4000 miles. I have only done 3 so far. As far as taking it to the dealer you can change it yourself. All you need is a 17mm socket. Drain pan. And some cloth to keep you clean..hehe..If you do change it yourself keep it documented just in case...I keep all my oil change receipts and write down the mileage and date i changed it and keep it inside the Car booklet inside the car drawer.