Pantherman is quite right, about all you can do is sand it all the way off and then add something corrugated. Depending on the length, you might be able to use a matched pair of gears, like the scrapbookers use for corrugating paper.

The other alternative is to sand it off and NOT replace it, and just finish the thing as-is. You said you're still a beginner, so chances are good that something else will go wrong. Use this kit as a test bed, then build another. You'll discover where the kit's weaknesses are (maybe your's as well.)

It's disappointing, but don't beat yourself up about it too much.

I'm ALWAYS screwing up models- that's why I usually like to build old, less expensive "beater" kits, just to see what I can make with them. I have some better, more expensive kits, but those I'm saving until I become an "expert," which at the rate I'm going will be when I'm around 135 years of age (I'm 64 now, btw) Good luck!