OK well 1 week ago I change my oil and now the warning light came on now after about 1000 miles why would it be low after a 1000 mile if its not leaking oil and the truck has only 65000 miles on it?

And should I take it to a dealer, and if so how much would that cost in southern CA or is it something that I could do myself?

You can add it yourself if you know exactly where to fill it and you do NOT over fill it.
It could be burning oil or it could possibly be leaking such a small amount that you do not see it. Hopefully you don't need a valve job or something.

ok well 1 week ago i change my oil and now the warning light came on now after about 1000 miles why would it be low after a 1000 mile if its not leaking oil and the truck has only 65000 miles on it??

and should i take it to a dealer, and if so how much would that cost in southern CA or is it somthing that i could do myself?
Which warning light came on?
There are three: oil change reminder, oil level and oil pressure.
If the oil level is on, but you know the level is correct by the dipstick, the oil level sensor may have failed. Call your local dealer for a price on this repair. The part is relatively inexpensive, but labor rates vary significantly from region to region.
I hope this helps.

If it's only the "Change Oil" light that's coming on, it's very possible that whoever changed the oil never reset the light. This can be done by turning the key to the on position, then depressing and releasing the accelerator pedal 3 times within 5 seconds. The light should then blink, indicating that the oil life has been reset.