You've got the cash, that's cool. You're finally determined, that's even more important. What you need to do now is to learn! Take your time, go to Youtube and watch all (and I mean all) the home-studio related videos. (That's what I did...) You can't setup an ideal home studio without knowing what your dream home studio would look like.
First go watch this video and then go on reading..
You have to choose:
1. a computer
2. a DAW
3. an Interface
4. a Mic
5. Monitors
and (6) you have to build a comfortable workstation!
1. I'd go with PC just because it's more powerful for the same price!
2. You can go on using FL, but I don't recommend it, you'll quickly find it's limitations...
3. Your current interface needs to go, look into it, get something decent, I totally recommend the older M-audio interfaces with two line ins and to mic pre-amps.
4. You've got an SM58 that's great use it for live, mic up guitar amps whatever, but for recording vocals, you'll need a large-diaphragm condenser mic, you heard the guy, don't go crazy, get something nice for $100-$200... (The RODE mics are dope)
5. If you can afford it get both headphones and monitors, helps a lot to have both. For headphones I recommend the AKG, Shure, the Sennheisers are nice too. For monitors I'd go with the krk rokit 6, (the 5s don't really have a decent low-end) or you can also get great M-audio or Yamaha, maybe RCF monitors. (Don't go cheap with monitors, you really wanna get a nice pair that you can use for years!)
6. Get a nice desk, hang some acoustic foam panels on the walls, get good mic-stands, a guitar rack maybe, good quality cables etc.. (spend a little money on making your studio comfortable...)
And the last but not least, make great songs, have fun, do what you like to do! Put together a few songs, try to find some guys for your band play some local gig. (btw you totally don't need a label to get money)
Almost forgot, you've go $7000 DON'T BLOW IT!