Moped Army

Well, I looked at the wiki, and see how it goes, but I've never done anything like this before and don't want to mess it up. Do I just draw on the cylinder with a sharpie or something and then have at it? What if I accidentally grind too much off? Is there a tolerable amount of messing up allowed, or will I ruin the cylinder? If I do the port job on the cylinder, is it required to do the porting on the crankcase too?

I'm not really looking for someone to hold my hand through the whole process, but some tips from someone that's done this before would be great.