oil change at 2000 miles???

[79 300CD]

If I haven't driven my diesel 3000 miles in the last year should I change the oil anyway? Or should I wait until I get the mileage? The oil is not low, but I was wondering if I just need to get it out and start over. The reason that I haven't driven much is because when it rains I am getting water standing in the left rear floorboard and when I think it's a remote chance of rain I won't drive it att all. This year we have been getting quite a bit of rain. I rather be safe. I have read many posts about the water problem but am a novice and can't seem to find out where the problem lies.