2008 Honda Accord Changing the oil in my car, question.

I just realized my washer slipped out I thought it put it back in my car, but I was wrong. Which is making me know I have to do this again. I tightened my drain plug already though and no oil is leaking and I drove with it, I don't know im in a rut. My question was, I left my old oil filter in my car, cause I didn't have a wrench to pull it out. But since I already drained my car on oil I just put in new oil. Ok anyways straight to the question. Can I change my filter, with oil in my engine already? What happens if I overflow my engine on oil put.5 more quarts than was needed accidently? Is the washer very important if I forgot to install it even though my car isnt leaking?This is the first oil change on my car, and it said oil life is at 5% anyways. I don't know what to do.