If you're worried, then practice first. If you're like most people, you've got some junk electronics lying about. Practice on them. There are many online tutorials on how to solder, so you can learn the basics first that way.
Once you've built up some confidence, go for it. Use fresh solder (don't simply "reflow" what's there), but don't go overboard. If you've done a good job, the joint will be smooth and shiny. If it looks coarse and grainy, you didn't use enough heat, or moved something before the joint cooled. Reheat and try again. Avoid blobbing so much that you cause a short circuit with nearby joints.
It's not hard. Just work carefully and you (and your Mac) will be fine.