I'm a software engineer deciding to leave my first job out of college after 3 years. 

I've been taking phone calls and interviewing but I've reached 2 bottle necks.

One is that I don't have the time to schedule all these onsite interviews. They are typically full day events, and I've already taken off 2 days in the past 2 weeks to do them. 

The second is that I need to study for these interviews, but I haven't been able to find the time to really dedicate to this. (so far I've only been able to cram)

I'm very unhappy at work right now, so I'm considering just putting in my two weeks notice, cashing out my vacation days, and using my time to study and really focus on interviewing. However, I've always heard that it's bad to leave a job before you have another one. Does it really make me that much less attractive of a candidate?

If I do stay, how do I manage to schedule these interviews and study for them while still doing my day job?