My dealership told me to change my oil at 10,000 miles on my brand new ford fiesta?

I have a 2013 ford fiesta and my dealership told me that my car only needs to be changed every 10,000 miles.so before my first oil change, I waited til 10,000 miles. Then I was told that my dealership was wrong and now i've been doing it after every 3,000 miles. But i'm wonderin since I changed it after the first 10,000 miles, could that have messed up my engine somehow? It was brand new when I got it. Only had 25 miles on it

Why is my car jingling / rattling?

When I drive at low speeds there's a jingley/rattle noise, well it sounds like a cow bell coming from my passenger rear tyre area. At first I thought it was the heat shield but I had that fixed. Anybody know what it could be? There's noting loose underneath the car.
Thank you for any help given
Oh I have a 52 plate ford fiesta zetec.

Buying a new car with trashed credit?

I'm 21. I got a credit card when I was 18 to build credit, my ex Boyfriend ended up charging it up and I was never able to pay it off and he wouldn't pay it. So it got sent to collection, and it's been their for awhile! I started paying it off… I'm scared it ruined my chances of buying my first new car. My mom said she would co sign for me, but I'm still unsure about what to do. I'm looking for a basic small car, maybe a ford fiesta basic model, or the ford focus basic model. My dad also gets a discount through ups. So can anybody give me some advice. How much do you think my payments would be?

Would they sell me a car?

Any advice?