If the lens is under warranty, by all means check to see if it's covered. Assuming it's not, though, your first step needs to be assessing the value of your lens. Go to ebay and see what these lenses are selling for used -- that's what you'd expect to be able to sell yours for if it's working. If you're going to consider sending the lens to be repaired, you want to consider that cost relative to what the lens is worth. If the repair ends up costing $200, for instance, are you comfortable investing that money in a lens that's worth barely more than that?

I had one of these lenses too, and mine started showing "Err01" at certain zoom lengths. It turns out this is a common problem stemming from a ribbon cable deep inside the lens that becomes pinched over time. Since this is a common problem, though, dis assembly / repair steps are pretty easy to find for this lens. You should be able to scare up all sorts of examples, but here are a few to get you started (1), (2), (3).

Before you attempt this repair yourself, you have to acknowledge that there's a real chance you'll fail, resulting in a collection of really interesting camera parts. Once you've got your head wrapped around that, though, the process isn't really too awful.

Preparation is key.

1. Line up a bunch of little containers for parts -- depending on how deep you have to go, you'll want up to 20-30 shallow cups, bowls, etc., to hold parts as you remove them. Use one container per step, and keep them in order.
2. Find a large, clean work area. You'll wind up needing more room than you might think.
3. Good lighting helps. Natural light might be best, but a work light that you can position where you want might be helpful, too.
4. Keep your lens cleaning kit handy. You'll avoid touching lenses as you work, obviously, but you may need to clean up a fingerprint as you go.
5. Since there are many reference documents online, pull up several of them and either print them or have them handy in your browser on a screen you can see well -- a laptop right in front of you will do nicely. It can be helpful to see photos from multiple angles / sources, so don't be afraid to compare different versions of this procedure.
6. As you work, note how the parts of the lens move, and make sure they still move that way when you reassemble. I ended up re-doing the assembly because I buggered up the zoom action the first time.

In your case, I'd expect that you won't have to do nearly as much work to find your problem as I did to replace that cable, but the instructions for dis-assembly / reassembly should apply in either case.

And in case you're wondering, mine worked just fine once I put it back together. I'd already replaced it with a new 15-85 lens, so I listed it for sale (noting the repair I'd made) and sold it for considerably more than the price of a paperweight, which was what it was before the repair.