I want to take off the oil finish on my Warwick Corvette FNA and put on a darker one.What number of sandpaper should i use,an 0000 maybe or harder?The wood is flame maple.

Sandpapers are graded in a number scale beginning at 20 or so (coarsest) and going up to 8000 or so (finest). The 0000 number you refer to might be a steel wool grade.

You could do a good job with 600 grit paper to get the top coating off but remember that oil penetrates the grain so there will be quite a bit of sanding if you want to eliminate all of the oil that is deep in the wood.

I'd probably start with something coarser than 600. Probably even 320. Who knows how deep the oil has penetrated. I don't have much patience for sanding. ;)

How are you going to apply the new stain? Keep in mind that a penetrating dye has to get through whatever is already there, and that, for example, a water based stain won't want to mix with oil that's already there.

600 grit will give you a smooth surface, but it will clog real fast, which means that you'll use a million sheets just to get down to the wood. 80 grit will clog a lot less, but sanding out the sanding scratches may cause you to spend just as much time as using a million sheets of 600 grit.

I would start with about 250-300 grit, for faster removal with minimal scratches, then work my way back to 600-800 grit... depending on what the current wood/finish looks like, and what you want the final wood/finish to look like.

Use the 0000 (called "four-ought") steel wool between the new coats of oil.