Not sure about the oil change miles - my manual says change the oil at 300, 3750, 7500, 11250, etc. - every other service interval listed. I recall discussion about whether that was a misprint. I'll let somebody more experienced opine whether you're in trouble or not.
But I will say that changing the oil is dirt easy; based on what you've told us about what you've done with your bike so far, you will easily be able to do it. If you can't get a filter in a hurry, PM me - I've got most of a 5-change kit on the shelf and I can front you the filter and gaskets you need...