Help I did it again!

I think the car has been sitting for a couple of years and being run once in a while. One thing that makes me think this is that the oil is clean but I just noticed on the oil filter Milage a few hundred less than on the Odometer and a date of 2005! I am not believing what the guy has told me about anything so when he said it has been sitting for a while I think it has been years. By the way the gas looks clean but it does smell old and there was dirt in the filter. THANKS EVERYONE FOR THE HELP HERE! With everyones help I am going to get this thing going