It's been said before - but i just finished replacing the head/bottom gaskets - and these are pretty much the simplest engines you'll ever work on. Aside from some doubt initially that i got the cam right (i did) that was about it.
One thing i can recommend is to pick up a box of freezer baggies. As you take things apart, keep the parts in the baggies, and label them where they came from, and with numbers from when. (ie: first bag will usually be "air box" and "1") Then when you're putting things back together, just go backwards.
Take pictures with a cheap digital camera. a *lot* of pictures. Pictures of how things looked before you took things apart, as you're taking it apart, how stuff was routed, what wire colours were plugged where, etc etc. Makes things a lot easier, especially if it's been a week since you took it apart.
Above all - DON'T PANIC. I started mine today as soon as i got it in the frame with the carbs on, and the wires hooked up, just to see if it would, or would require pulling it back out. Fired up fine. Then after getting the airboxes and exhaust back on, tried it again. Wouldn't start. Couldn't figure it out. Swapped plugs, checked for spark, had fuel... Turns out i had pulled the throttle cable a bit and the butterflies were open enough that it wouldn't start (for whatever reason, mine won't start cold unless the butterflies are totally closed - which is fine, really). Something that simple can sometimes cause you huge worries. just remember "DON'T PANIC" and you'll be fine.