@OP, in terms of burnout I'm pretty much in the same boat. Taking CFA/CPA concurrently, and it's tough. I wouldn't recommend it unless there's some serious babysitting/child care assistance in the near future.
That beng said, if you have your MSF, Level I won't present many problems for you. Levl II is defintely tougher, but most of the material should be familiar. The difficult part is the question format, volume of material, and the depth of understanding.
Level III is where you'll probably presented with many new concepts and an essay format. It's tough, but I've heard Level II is tougher.
If you're still on the fence I'd recommend checking out the material on investopedia. They have a free online study guide (albeit a bit outdated, but 80% is still relevant) for Level I. I'd say that if you feel you have a really good grasp of the concepts and have some energy, then go for Level I. Remember, this is a marathon , and not a sprint.
Unlike the CPA exams, the CFA credits don't expire, and many people take years to get the certification. So don't feel like it's a "now or never" situation. That being said, as a fellow burnout, I'd recommend taking some time away from studying. The itch to hit the books will come with time or not at all. If the latter, then it probably wasn't going to happen anyhow.
Also, to the poster who mentioned that the CFA might not have much relevance to Corp. Finance, I have to politely disagree with the people who told her that. Of course, the use/benefit totally depends on the specific company you work for. I've worked at firms where it is highly valued because the hiring manager had the charter. Having it also gives you tons of kudos from the finance community no matter what you do. Yah, many people in equity research, asset mgt, security analysis, and portfolio management already have it, but you don't see a lot of it in corp finance.
Obviously, if you say "CFA" and you get blank stares at your firm then there's not much benefit there. But don't rule out it giving you a bump in the future for a different firm or position. Hell, your current firm might even merge with another firm that can use someone with that background. Just saying that the effect goes beyond the inital obtaining of the charter, and can give lots of long term benefits.