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Like I say, it's only a little bit. You'll notice the difference on a few of the corners, but the longish straight sections probably still need more touching up.
So, to use this, open your track in traxx, and on the edit menu select copy terrain as bitmap. Then in your paint program, paste and you should see a graphic similar to above. Save it as a bmp or a gif file. This is for back up purposes in case you don't like the new one.
Now, for the new one, open it in your paint program and copy it to the clipboard. With traxx still open, on the edit menu select paste terrain bitmap. If you have your eye on the terrain, you might notice the slight change.
Pod it up and have a look. If you like it, you can continue working on it. If you don't, just follow these same steps to put your original one back. (alternately, you can save a new txx as a temp file while you try it out, and just delete it if you don't like it).
If this was my track. What I'd do is work on about ten to fifteen squares along the road at a time. I'd make some changes then go try in it game. I wouldn't even close traxx. Then, after trying it, I'd do a bit more. When I'm happy with that section, I would move up another ten squares or so. I often bring the first truck along with me because driving up to the middle parts of the track can be very time consuming. Once you have gone all the way around the course, the truck will be back at the beginning anyway, so there's no harm in saving yourself some time. But basically, that's all there is to it. Just take your time, little by little, section by section, and you can make a nice driving course... or at least one that you're satisfied you've done all you can.
Hope this helps.