Jumping in with both feet or baby steps?

I'd recommend the baby steps, but use the motivation you have starting out to try out a bunch of different baby steps. Here are some pieces of advice I've gathered from people who seemed to be successful at their goals (usually weight loss, but for some weight gain or greater fitness or... you pick): http://www.myfitnesspal.com/blog/Robin_Bin/view/how-to-use-myfitnesspal-427993
But I realize when you first start, you're often highly motivated and want to see at least some results. Start by being very good at logging -- measure, weigh, count -- learn about food and nutrition. If that makes you feel like eating a bit differently to match the target macros or exercising a bit more so you con log it, great! Try out some other things -- new foods, new routines or new exercises. Over time you'll learn what works for you. But trying to make it all work or getting to extreme about everything is probably setting yourself up for disappointment.

People keep telling me to take it slow. Just log food for now, worry about the rest later. Don't try to lose so much at first, get settled into dieting. etc etc.

But I feel like if I don't jump in with both feet and just get going on everything now, I will just let myself fall back into old bad habits that got me where I am today (almost 150lb overweight)...

Anyone feel the same or can offer advice?

I think that is sound advice when it comes to dieting. Nearly all of us are addicted to sugar and/or salt so to just cut those things for most people is extremely hard and then when they fail they tend to quit thinking I can't do this. To ask yourself to do too much at once in my opinion can be setting yourself up to fail unless you are extremely stubborn minded. So it all depends on your mindset and your will power. If you can push through the times you wobble and not let it hinder your progress then go ahead go all out but if you tend to get discouraged easily then take it slow.
I would recommend making some small daily or weekly, monthly goals and also figure out some big long term goals.