Are you really going to retake it even with a near perfect score in the other sections?
Well, that's your choice, but here's my advice on the writing. I just finished a GRE prep course (no, I don't have the $$ for that! It was free as a part of an undergrad fellowship). It would really help to pair up with a friend or two and practice. Read the prompt, work silently for 30 minutes, then review the pro/con lists you each made, or the list of assumptions made, or whatever your outlining strategy might be. This was helpful for me because I was able to get fresh perspectives and see what I missed. It helped me think more broadly, and it helped my friends think more specifically. Good for everyone. It probably helped that I had some philosophy folks in there, so if you know any friends in that major, that wouldn't hurt!
As far as the writing itself, I've been told there is a "safe" formula to follow to get you a decent score on the analyze an argument. It's basically the five paragraph essay we learned in like middle school. Intro, point 1, point 2, point 3, conclusion. I've also been told to do six paragraphs, where I list three points, and one counterpoint. But spread them out so it goes intro, point 1, point 3, counterpoint, point 2 (rebuttal to the counterpoint), conclusion. With the analyze an issue, it's not about whether or not you agree. It's pulling apart the assumptions made in the argument. The more you practice the more obvious the assumptions will be. They're usually really bad, for example drawing conclusions from data that doesn't represent the issue.
Spend at most 5 minutes brainstorming and outlining. Longer essays are correlated with higher scores so give yourself enough time to write all your thoughts. And spend the last minute or so proofreading for obvious errors.
All the practice essays are on the GRE website. You will not see one on the test that isn't on that website. So practice them from there. Also, although it's obvious, make sure to closely follow the instructions. Apparently the newer GRE has varying instructions from question to question. Some specifically ask you to bring up counterpoints, some ask you to consider what evidence is needed, etc. They vary so just do exactly what it says.